Abstract: The invention provides a method for the preparation of 2-cyclopenten-1-one derivatives. The process involves metalating 2-methylfuran in the 5-position by an interchange reaction with an alkali metal-organic compound, condensing the resulting metal derivative of 2-methylfuran with a halide of the formula R--CH.sub.2 --X, wherein R represents an unsubstituted acyclic hydrocarbon radical which is free of triple bonds, comprises from 0 to 2 double bonds and contains from 3 to 5 carbon atoms and X represents a halogen, in order to form a 2,5-disubstituted furan of the formula ##EQU1## treating the disubstituted furan with an acidic agent to cause the opening of the furan ring and the formation of a dione of the formula ##EQU2## and cyclizing the dione by a treatment with alkali.

Abstract: The present invention relates to a novel process for preparing unsaturated aldehydes comprising four double bonds of formula ##SPC1##Wherein one of the double bonds is represented by the dotted lines. Aldehyde Ia (called .alpha.-sinensal) corresponds to the above formula wherein the double bond represented by the dotted lines is in the main carbon chain. Aldehyde Ib (called .beta.-sinensal) corresponds to the above formula wherein the double bond represented by the dotted lines is in the side chain. The invention also relates to new intermediates used in the said new process and to methods for preparing them. The said intermediates have also valuable organoleptic properties and are useful as fragrances in the preparation of perfumes, perfumed products and artificial essential oils.

Abstract: The present invention relates to a novel process for preparing unsaturated aldehydes comprising four double bonds of formula ##SPC1##Wherein one of the double bonds is represented by the dotted lines. Aldehyde Ia (called .alpha.-sinensal) corresponds to the above formula wherein the double bond represented by the dotted lines is in the main carbon chain. Aldehyde Ib (called .beta.-sinensal) corresponds to the above formula wherein the double bond represented by the dotted lines is in the side chain. The invention also relates to new intermediates used in the said new process and to methods for preparing them. The said intermediates have also valuable organoleptic properties and are useful as fragrances in the preparation of perfumes, perfumed products and artificial essential oils.

Abstract: New process for the preparation of cyclic ketones possessing interesting organoleptic properties and including methyl 2-(cis-pent-2-enyl)-3-oxo-cyclopentylacetate and 3-methyl-2-(cis-pent-2-enyl)-cyclopent-2-enone, better known in the perfume industry as cis-methyl jasmonate and cis-jasmone respectively.

Abstract: New heterocyclic derivatives containing nitrogen useful for perfumery and the flavour industry and use of same as perfuming and/or flavouring ingredients in the manufacture of perfumes and perfumed products and/or in the preparation of artificial flavours for foodstuffs, beverages, animal feeds, pharmaceutical preparations and tobacco products.Process for preparing the said heterocyclic derivatives which are equally useful as starting materials for preparing known fragrance compounds.