Abstract: Process for synthesizing a chemical, in particular an agriculturally or pharmaceutically active compound, including: a first step comprising reacting a carboxylic acid halide with a vinyl ether to prepare a halogenated precursor of an alkenone; a second step comprising eliminating hydrogen halide from such precursor to form an alkenone, preferably by thermolysis under specific conditions; and a third step which uses the formed alkenone as a building block to synthesize the chemical. First step may be done in a liquid reaction medium comprising an alkenone or a halogenated alkenone precursor, or in a liquid reaction medium in turbulent state, specifically by creation of gas bubbles of the carboxylic acid halide herein. Second step may include a flash thermolysis, vacuum thermolysis, thermolysis under stripping with inert gas, and/or a thermolysis at a temperature from >90° C. to 120° C. Third step preferably comprises reacting the alkenone with a nitrogen-containing compound.

Abstract: Ketones, specifically Methyl ethyl ketone (“MEK”) and octanedione, may be formed from six carbon sugars. This process involves obtaining a quantity of a six carbon sugar and then reacting the sugar to form levulinic acid and formic acid. The levulinic acid and formic acid are then converted to an alkali metal levulinate and an alkali metal formate (such as, for example, sodium levulinate and sodium formate.) The alkali metal levulinate is placed in an anolyte along with hydrogen gas that is used in an electrolytic cell. The alkali metal levulinate within the anolyte is decarboxylated to form MEK radicals, wherein the MEK radicals react with hydrogen gas to form MEK, or MEK radicals react with each other to form octanedione. The alkali metal formate may also be decarboxylated in the cell, thereby forming hydrogen radicals that react with the MEK radicals to form MEK.

Abstract: A process for producing diisobutyl ketone (DIBK) which includes bringing together triacetone dialcohol (TDA) and a bifunctional catalyst that can perform a dehydration and hydrogenation reaction is described.

Abstract: A process for preparing a halogenated precursor of an alkenone, which comprises reacting a carboxylic acid halide with a vinyl ether in a liquid reaction medium under turbulent conditions and a process for preparing an alkenone, by eliminating hydrogen halide from said precursor to form the alkenone.

Abstract: The present invention relates to a continuous process for producing a haloalkenone ether of the Formula (I) wherein R1 is C1-C6 haloalkyl, R2 is a C1-C6 alkyl or phenyl, the process comprising:—(i) reacting, in a first continuous stirred tank reactor comprising a solvent, a halide of Formula (II) wherein R1 is as previously defined and R3 is halogen, with a vinyl ether of Formula (III) wherein R2 is as previously defined, to form an intermediate compound of Formula (IV), wherein the concentration of the vinyl ether of Formula (III) in the reaction mass is 15% or less w/w; and (ii) transferring the reaction mass from the first continuous stirred tank reactor into a subsequent continuous stirred tank reactor, wherein the conditions within the subsequent reactor permit the elimination of hydrogen halide (HR3) from the intermediate compound of Formula (IV) to provide the haloalkenone ether of Formula (I).

Abstract: A process for producing diisobutyl ketone (DIBK) which includes bringing together triacetone dialcohol (TDA) and a bifunctional catalyst that can perform a dehydration and hydrogenation reaction is described.

Abstract: Process for preparing an alkenone, which comprises (a) reacting a carboxylic acid halide with a vinyl ether by introducing vinyl ether into a liquid reaction medium containing carboxylic acid halide to form a halogenated precursor of the alkenone and (b) eliminating hydrogen halide from said precursor to form the alkenone.

Abstract: Process for preparing an alkenone, which comprises the following steps: (a) providing a halogenated precursor of the alkenone; and (b) eliminating the hydrogen halide from said precursor to form the alkenone by a thermolysis treatment selected from the group consisting of flash thermolysis, vacuum thermolysis, and thermolysis under stripping with inert gas.

Abstract: A process for preparing a halogenated precursor of an alkenone, which comprises reacting a carboxylic acid halide with a vinyl ether in a liquid reaction medium comprising an alkenone or a halogenated precursor of the alkenone, and a process for preparing an alkenone, which comprises (a) reacting a carboxylic acid halide with a vinyl ether by introducing vinyl ether into a liquid reaction medium containing carboxylic acid halide to form a halogenated precursor of the alkenone and (b) eliminating hydrogen halide from said precursor to form the alkenone.

Abstract: A process for preparing a halogenated precursor of an alkenone, which comprises reacting a carboxylic acid halide with a vinyl ether in a liquid reaction medium comprising an alkenone or a halogenated precursor of the alkenone, and a process for preparing an alkenone, which comprises (a) reacting a carboxylic acid halide with a vinyl ether by introducing vinyl ether into a liquid reaction medium containing carboxylic acid halide to form a halogenated precursor of the alkenone and (b) eliminating hydrogen halide from said precursor to form the alkenone.

Abstract: A process for preparing a halogenated precursor of an alkenone, which comprises reacting a carboxylic acid halide with a vinyl ether in a liquid reaction medium under turbulent conditions and a process for preparing an alkenone, by eliminating hydrogen halide from said precursor to form the alkenone.

Abstract: A low-pressure one-step gas-phase process for the production and recovery of methyl isobutyl ketone (MIBK) is disclosed. One-step gas-phase synthesis of MIBK from acetone and hydrogen over nano-Pd/nano-ZnCr2O4 catalyst at atmospheric pressure is used as an example. The said process is designed to recover the additional heat associated with the reactor effluent via heating acetone feed and recycle (mixed acetone) before entering the reactor. A compressor is introduced to the gas-phase process to increase slightly the reactor effluent pressure before this effluent is cooled and fed to a flash drum. The compressed reactor effluent is used to preheat hydrogen feed and recycle (mixed hydrogen) before entering the reactor. The separation scheme of low-pressure one-step gas-phase process comprises of several distillation columns used for MIBK separation and purification.

Abstract: Aldehyde and ketone reactants are converted to hydroxyaldehydes, polyhydroxyaldehydes, hydroxyketones and/or polyhydroxyketones in liquid phase by an aldol condensation process where a selected product carbon chain length is produced using specific concentrations of soluble inorganic base at sub-ambient temperature.

Abstract: Disclosed is a process of preparing an optically active ?-hydroxycarboxylic acid derivative comprising asymmetrically hydrogenating a ?-keto compound in the presence of a catalyst comprising a transition metal complex compound having a 2,3-bis(dialkylphosphino)pyrazine derivative as a ligand. The pyrazine derivative is preferably a quinoxaline derivative, and the transition metal is preferably ruthenium. Preferred examples of the quinoxaline derivative are (S,S)-2,3-bis(tert-butylmethylphosphino)quinoxaline, (R,R)-bis(tert-butylmethylphosphino)quinoxaline, (S,S)-bis(tert-adamantylmethylphosphino)quinoxaline, and (R,R)-bis(adamantylmethylphosphino)quinoxaline.

Abstract: The present invention relates to a process for the preparation of compounds of a 1,4-dialkyl-2,3-diol-1,4-butanedione by a catalytic aldol condensation between an alkyl glyoxal and an ?-hydroxy ketone.

Abstract: A two-step aldol condensation process is disclosed. ?-Campholenic aldehyde (ACA) and methyl ethyl ketone (MEK) react in the presence of a base under conditions effective to produce a mixture comprising a high yield of ketol condensation products. Dehydration of the ketols in the presence of an organic sulfonic acid provides unsaturated ketones that are valuable intermediates for fragrance components for synthetic sandalwood products. Compared with the usual one-step, base-catalyzed approach, the two-step process increases the yield of all condensation products and maximizes production of the most valuable ketone isomers.

Abstract: Continuous single-step processes for producing higher molecular weight ketones are disclosed that involve a liquid-phase crossed condensation of an aldehyde with a ketone in the presence of a hydrogenation catalyst and a small amount of a catalyst comprising a concentrated hydroxide or alkoxide of an alkali-metal (from Group 1 or Group IA of the Periodic Table of the Elements) or alkali-earth metal (from Group 2, or Group IIA of the Periodic Table of the Elements), wherein the amount of water provided to the reaction mixture, or reaction zone, is relatively low, with respect to the total initial weight of the reaction mixture. The reaction may be carried out in the absence of solubilizing agents or phase transfer agents. The product mixture is largely free of by-products resulting from further condensation reactions of the desired ketone product or intermediates, and free of the self-condensation products of the reactant aldehyde, that are afterward difficult to remove from the reaction mixture.

Abstract: A method for preparing ketones in greater yield and selectivity compared to previous catalyzed reactions by acid-catalyzed condensation reaction using a metal-doped polysulfonated ion exchange resin catalyst is disclosed. For example, use of polysulfonated ion exchange resins having at least 5.0 milliequivalents sulfonic acid groups/gram catalyst and loaded with metal, such as palladium, provides enhanced yields of methyl isobutyl ketone from the condensation reaction of acetone compared to use of conventional monosulfonated ion exchange resin catalysts.

Abstract: Processes for producing ?-hydroxy-ketones and ?,?-unsaturated ketones are disclosed which comprise the crossed condensation of an aldehyde with a ketone in the presence of a hydroxide or alkoxide of alkali metal or an alkaline earth metal as catalyst. The products of the process, ?-hydroxy-ketones and ?,?-unsaturated ketones, are useful for the preparation of many commercially important products in the chemical process industries including solvents, drug intermediates, flavors and fragrances, other specialty chemical intermediates.

Abstract: A process is provided for the production of acetone from formaldehyde and methyl chloride. In the process formaldehyde is reacted in the vapor phase with methyl chloride to produce acetone and hydrogen chloride. Acetaldehyde may be formed as an intermediate in the reaction. The byproduct hydrogen chloride may be recovered from the process to produce additional methyl chloride from methyl alcohol.

Abstract: One aspect of the present invention relates to methods for the transition-metal-catalyzed asymmetric 1,4-addition of a nucleophile, e.g., hydride, to cyclic and acyclic enoates and enones. In certain embodiments of the methods of the present invention, the transition metal catalyst consists essentially of copper and an asymmetric bidentate bisphosphine ligand.

Abstract: A process for producing 1,1,1-trifluoroacetone includes the step of conducting in a gas phase a hydrogenolysis of a tetrafluoroacetone, which is represented by the general formula [1], by a hydrogen gas in the presence of a catalyst containing a transition metal, where X represents a chlorine, bromine or iodine, and n represents an integer from 0 to 2.

Abstract: A process for producing methyl isobutyl ketone includes introducing acetone into a catalytic distillation. Some of the acetone is converted to mesityl oxide (‘MSO’), water and, optionally, diacetone alcohol (‘DAA’) and/or other by-products. A product stream comprising MSO, water, and, optionally, DAA, other by-products and/or unreacted acetone is withdrawn from the catalytic distillation zone. When the product stream includes DAA, other by-products and/or unreacted acetone, it is treated in a treatment zone to remove at least some of the DAA, other by-products and/or the unreacted acetone therefrom. The product stream and hydrogen are fed into a reaction zone in which MSO present in the product stream and hydrogen react to form methyl isobutyl ketone (‘MIBK’). A MIBK rich product stream is withdrawn from this reaction zone. Both a markup and clean copy of the substitute Abstract are attached to this amendment.

Abstract: A process for the preparation of methylheptanone and corresponding homologous methyl ketones involves the cross-aldolization of acetone with the corresponding aldehyde. The polar catalyst phase is introduced with acetone and an organic auxiliary solvent phase to form a two phase mixture in the presence of hydrogen. The corresponding aldehyde is then added at temperatures between 40° C. and 200° C. The process can be run in a continuous manner with the polar catalyst phase being recyled after regeneration. The use of the non-polar auxiliary solvent(s) increase yield and selectivity.

Abstract: Methylheptanone and corresponding homologous methylketones, in particular phytone and tetrahydrogeranyl acetone, are produced by aldol condensation of isovaleraldehyde or prenal or the corresponding aldehydes with acetone in the presence of a catalyst phase, which contains an aldolizing catalyst and a heterogeneous hydrogenating catalyst.

Abstract: A process for producing methyl isobutyl ketone includes introducing acetone into a catalytic distillation. Some of the acetone is converted to mesityl oxide (‘MSO’), water and, optionally, diacetone alcohol (‘DAA’) and/or other by-products. A product stream comprising MSO, water, and, optionally, DAA, other by-products and/or unreacted acetone is withdrawn from the catalytic distillation zone. When the product stream includes DAA, other by-products and/or unreacted acetone, it is treated in a treatment zone to remove at least some of the DAA, other by-products and/or the unreacted acetone therefrom. The product stream and hydrogen are fed into a reaction zone in which MSO present in the product stream and hydrogen react to form methyl isobutyl ketone (‘MIBK’). A MIBK rich product stream is withdrawn from this reaction zone.

Abstract: A method for oxidizing an alkane, comprising the step of oxidizing said alkane with oxygen in the presence of an aldehyde, a copper-based catalyst and a nitrogen-containing compound. This method may be used to convert alkanes to corresponding alcohols and ketone having pharmaceutical activities, etc.

Abstract: One aspect of the present invention relates to methods for the transition-metal-catalyzed asymmetric 1,4-addition of a nucleophile, e.g., hydride, to cyclic and acyclic enoates and enones. In certain embodiments of the methods of the present invention, the transition metal catalyst consists essentially of copper and an asymmetric bidentate bisphosphine ligand.

Abstract: The present invention provides a liquid phase process for the acylation of aromatic compound by an acylating agent of the formula (R5R6R7)—Y—Z to obtain the corresponding acylated compound using a solid catalyst comprising a metal oxide of the formula AOx with or without a catalyst support, wherein A is a metallic element selected from Ga, In, Ti, Fe and a mixture of two or more thereof, and x is the number of oxygen atoms required to fulfil the valance requirement of A, wherein the catalyst is pretreated with a dry gas comprising a hydrogen halide in the presence or absence of the aromatic compound to be acylated, contacting the hydrogen halide pretreated catalyst with a liquid reaction mixture comprising the aromatic compound and the acylating agent, cooling the reaction mixture, removing the catalyst from the reaction mixture and then separating the reaction products from the reaction mixture.

Abstract: Preparation of cyclic, &agr;,&bgr;-unsaturated ketones of formula II by dehydrogenation of cyclic ketones which conform to formula I in which n denotes an integer from 1 to 10, and which may be substituted, at elevated temperature in the presence of catalysts in the vapor phase, wherein the reaction is carried out in the absence of oxygen or in the presence of less than 0.5 mol of oxygen per mol of compound I at temperatures ranging from 250° to 600° C. and using catalysts having a surface area (BET) of more than 0.5 m2/g.

Abstract: The present invention provides a process for producing 6-methyl heptanone and corresponding methyl ketones, in particular phytone and tetrahydrogeranyl acetone, by aldolization of aldehydes with acetone in the presence of an aldolization catalyst and a heterogeneous hydrogenation catalyst containing a polyhydric alcohol.

Abstract: A process for preparing ketones by so-called “crossed aldol condensation” of a ketone with an aldehyde in the presence of a catalyst system consisting of approximately equimolar amounts of a secondary amine and of a carboxylic acid containing at least 2 C atoms, to form an &agr;,&bgr;-unsaturated ketone, and, where appropriate, subsequent catalytic hydrogenation. The process is used in particular for preparing 6-methyl-3-hepten-2-one by reacting acetone with isovaleraldehyde, and for preparing its hydrogenation product, 6-methylheptan-2-one, which is an important precursor for numerous active substances, in particular for preparing lipid-soluble vitamins such as vitamin E.

Abstract: An entirely aqueous method to prepare cyclopropyl methylketone from acetyl-propanol. The method is practiced by (1) forming a mixture of acetyl-propanol and an aqueous hydrogen halide, (2) distilling the mixture and returning at least a portion of the distillate that is aqueous to the distilland, (3) recovering 5-halo-2-pentanone from the distillate, and (4) reacting the 5-halo-2-pentanone with a basic solution that is from about 1-wt % to about 25-wt % base and about 75-wt % to about 99-wt % water to yield cyclopropyl methylketone.

Abstract: In order to make it possible to produce 6-methylheptan-2-one, which is useful as a material for synthesizing isophytol or as a material for synthesizing fragrances such as tetrahydrolinalool and dihydrogeraniol, efficiently and in an industrially simple manner, isovaleral and acetone are subjected to aldol condensation in the presence of a basic substance to form a condensate which contains 4-hydroxy-6-methylheptan-2-one, and then the condensate is subjected to hydrogenation reaction under a dehydration condition to obtain the 6-methylheptan-2-one.

Abstract: A multistep process for producing amyl ketones is provided. In the process, a methyl ketone is reacted with butyraldehyde to form a C.sub.7 aldol condensation product which is then dehydrated to form an olefinic ketone and hydrogenated to form an amyl ketone. The process is suitable for coproduction along with the production of MIBK and yields products with a high selectivity.

Abstract: Disclosed herein is a process for producing a .gamma.-hydroxyketone (2), which comprises asymmetrically hydrogenating a .gamma.-diketone (1) in the presence of a ruthenium-optically active phosphine complex as a catalyst ##STR1## wherein R.sup.1 and R.sup.2 mean individually an alkyl or phenyl group which may have a substituent group. According to the invention, optically active .gamma.-hydroxyketones useful in synthesizing optically active moiety in, biodegradable polymers, perfumes, intermediates for synthesizing medicines and the like can be efficiently prepared.

Abstract: The present invention provides a method of preparing sodium formyl acetone using acetone, methyl formate and sodium methoxide as raw materials. A mixture consisting of an acetone and a methyl formate is supplied to a methanol solution of sodium methoxide, or an acetone and a methyl formate are separately supplied simultaneously to the methanol solution of sodium methoxide. The resultant mixture is sufficiently stirred over a predetermined period of time so as to carry out the reaction to form sodium formyl acetone. Also provided is a method of preparing 4,4-dimethoxy-2-butanone. In this method, the reaction mixture obtained in the reaction to form sodium formyl acetone is directly charged into a reaction vessel simultaneously with sulfuric acid to neutralize and acetalize sodium formyl acetone contained in the reaction mixture so as to obtain 4,4-dimethoxy-2-butanone.

Abstract: This invention relates to a process for preparing fluoropolyethers and perfluoropolyethers having neutral and/or functional end groups and a lower molecular weight by a selective catalytic cleavage of the corresponding higher molecular weight fluoropolyethers and perfluoropolyethers, characterized in that said cleavage is carried out by operating in the presence of a catalyst system consisting of a combination of silicon dioxide with at least an oxide, a fluoride or an oxyfluoride of a metal selected from Al, Ti, V, Cr, Co. Fe, Ni, Mo, Zn, Cu, Cd, Mn, Sb, Sn, Zr, Sc, Y, La and homologs thereof, Pb, Mg, W.

Abstract: The process for the production of high molecular weight oxygenates by condensing low molecular weight oxygenates in the presence of CO and a catalyst having the general formula A.sub.a CuM.sub.c X.sub.d O.sub.x. In addition, a novel condensation catalyst comprising A.sub.a CuM.sub.c Bi.sub.d O.sub.x is disclosed for use in this process.

Abstract: A process for the production of 4,6-dimethyl-7-hydroxynonan-3-one of specific stereochemistry is disclosed. The process results in an active (+)-serricornin.

Abstract: Alpha,beta-unsaturated ketones of the formula (I) ##STR1## where R.sup.1, R.sup.2 and R.sup.3 are each hydrogen, alkyl, alkenyl of 1 to 12 carbon atoms, cycloalkyl, aryl, aralkyl or alkylaryl, are prepared by converting the corresponding .alpha.-hydroxy, alkoxy or carboxy compound in the presence of an acidic catalyst.Preferred starting materials are 3-methyl-3-hydroxy-butan-2-one, 3-methyl-3-hydroxypentan-2-one and 3-pentamethylene-3-hydroxypropan-2-one, and preferred catalysts are zeolites of the pentasil type.

Abstract: Novel .beta.-fluoroacyl-.beta.-halogenovinyl alkyl ethers of the formula ##STR1## in which R.sup.1 is a fluorinated alkyl group having 1 to 9 carbon atoms,Hal is a halogen atom, andR.sup.2 is an alkyl group having 1 to 7 carbon atoms,useful as insecticide intermediates, are produced by reacting a .beta.-fluoroacylvinyl ether of the formulaR.sup.1 --CO--CH.dbd.CH--OR.sup.2 (II)with a halogenating agent at a temperature of -70.degree. C. to +80.degree. C., to produce a halogenation product of the formula ##STR2## and dehydrohalogenating (III) at a temperature of -20.degree. C. to +100.degree. C.

Abstract: Ketones of the formula ##STR1## where R.sup.1 to R.sup.3 are each hydrogen and R.sup.1 to R.sup.4 are each alkyl of 1 to 12 carbon atoms, cycloalkyl of 4 to 8 carbon atoms, aryl, aralkyl or alkylaryl, which each in turn may be substituted, or R.sup.1 and R.sup.2 and R.sup.3 together with the carbon atoms to which they are bonded form a cycloalkane, are prepared by reacting ketones of the formula ##STR2## where one of R.sup.1, R.sup.2, R.sup.3 and R.sup.5 is hydroxyl, alkoxy or carboxyl while the remaining R.sup.1 to R.sup.4 have the abovementioned meanings, with hydrogen in the presence of acid catalysts supporting one or more hydrogenation components, zeolites of the pentasil type being particularly suitable.

Abstract: Bifunctional compounds of the formula ##STR1## where R.sup.1, R.sup.2 and R.sup.3 are each alkyl of 1 to 6 carbon atoms, R.sup.2 and R.sup.3 may furthermore be hydrogen, R.sup.2 is furthermore alkoxy and R.sup.4 is hydrogen, alkyl of 1 to 6 carbon atoms or alkoxy, and a double bond may be present between carbon atoms 2 and 3, are prepared by converting a tetraalkoxyalkane or a dialkoxyalkanoate of the formulae ##STR2## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 have the above meanings, in the presence of a catalyst, such as a zeolite, in particular one of the pentasil type, and/or a phosphate and/or phosphoric acid on a carrier.

Abstract: Chloro-olefins which contain a group of the formula ##STR1## where Y is chlorine or hydrogen, which are prepared by a process in which a trichloromethyl compound which contains a group of the general formula ##STR2## where X is hydrogen or an organic radical, is reduced with a chromium(II) salt in an aqueous medium.

Abstract: This invention pertains to a new method for killing and controlling worms (Helminths), new formulations for killing and controlling worms in animals, new chemical compounds, and a new synthesis of northern hemisphere intermediates for the synthesis of milbemycin and avermectin macrolides.

Abstract: A method for the dehydroxylation of alpha-hydroxyketone using lithium diphenylphosphide. The alpha-hydroxyketone, e.g. benzoin, is reacted with a solution of lithium diphenylphosphide followed by the addition of either an alkyl halide, e.g. methyliodide, or an alkyl halide and an organic acid, e.g. acetic acid, to yield the dehydroxylated compound, e.g. desoxybenzoin.

Abstract: The invention relates to a process for the preparation of glyoxal, alkylglyoxals and acetals thereof by reacting .alpha.,.beta.-unsaturated dialkylacetals with the equivalent amount of ozone and subsequently subjecting the ozonization products to catalytic hydrogenation, the peroxide-containing ozonization solution being fed continuously into a suspension of the hydrogenation catalyst, while a peroxide content of not more than 0.1 mole/liter is maintained, and cleaving the ozonization products by reduction, after which the dialkylacetals formed in the hydrogenation are, if desired, cleaved to give glyoxal or alkylglyoxals.

Abstract: Described is a process for preparing solanone and norsolanadione wherein in preparing solanone, the compound having the structure: ##STR1## or a mixture of compounds defined according to the structure: ##STR2## is reacted with methyl lithium and the resulting intermediate is hydrolyzed and the resulting compound is dehydrated and wherein in preparing norsolanadione this compound or mixture of compounds is reacted with ethylene glycol or propylene glycol thereby forming a ketal and the resulting ketal is reacted with methyl lithium and the resulting intermediate is then hydrolyzed in the presence of acid in which one of the dashed lines represents a carbon-carbon single bond and the other of the dashed lines represents a carbon-carbon double bond.

Abstract: Described is the genus of compounds defined according to the structure: ##STR1## wherein one of the dashed lines represents a carbon-carbon double bond and the other of the dashed lines represents a carbon-carbon single bond; wherein R.sub.4 represents methyl or ethyl; wherein one of R.sub.1, R.sub.2 and R.sub.3 represents 2-methyl-1-propenyl or 2-methyl-1-propylidenyl; and the other of R.sub.1, R.sub.2 and R.sub.3 represent hydrogen; with the provisos that:(i) when the dashed line at the 3-4 position is a double bond, then R.sub.3 is hydrogen or 2-methyl-1-propenyl;(ii) when the dashed line at the 2-3 position is a double bond, then R.sub.2 is hydrogen or 2-methyl-1-propenyl;(iii) when R.sub.4 is ethyl, then R.sub.2 is methyl and the double bond is at the 2-3 position; and(iv) when R.sub.4 is methyl, then R.sub.2 is hydrogen; 2-methyl-1-propenyl or 2-methyl-1-propylidenyl;with the members of said genus being novel compounds when R.sub.4 is ethyl or when R.sub.