Abstract: A method of increasing enantioselectivity in a reduction reaction of a prochiral substrate with a borane reagent including a borohydride species (for example, a borohydride stabilized borane-tetrahydrofuran complex) catalyzed by a chiral catalyst includes the step of maintaining the concentration of borohydride species in the borane reagent below approximately 0.005 M during the reduction of the prochiral substrate. A method of increasing enantioselectivity in a reduction reaction of a prochiral substrate with a borane reagent including a borohydride species that is catalyzed by a chiral catalyst includes the step of reducing the detrimental effect the borohydride species has on enantioselectivity by adding a Lewis acid. For example, the prochiral substrate can be a ketone and the chiral catalyst can be a chiral oxazaborolidine.
Type:
Grant
Filed:
January 26, 2001
Date of Patent:
August 26, 2003
Assignee:
Mine Safety Appliances Company
Inventors:
Karl Matos, Joseph A. Corella, II, Elizabeth R. Burkhardt, Shawn M. Nettles
Abstract: A method for synthesizing highly soluble metal alkoxides includes the step of reacting a tertiary alcohol having the formula:
wherein R1, R2, and R3 are, independently, the same or different, an alkyl group, an alkenyl, an alkynyl group or an aryl group, and at least one of R1, R2, and R3 is a group of at least 3 carbon atoms, with at least a stoichiometric amount of a metal reagent. The metal reagent is generally a group I metal, a group II metal, zinc, a metal alloy of a group I metal, a metal alloy of a group II metal, a metal alloy of zinc, a compound of a group I metal, a compound of a group II metal or a compound of zinc.
Type:
Grant
Filed:
May 30, 2000
Date of Patent:
September 3, 2002
Assignee:
Mine Safety Appliances Company
Inventors:
Elizabeth R. Burkhardt, Joseph A. Corella, II, David H. Ellenberger, Christopher P. Sutton
Abstract: A synthetic route for forming lithium trisubstituted borohydride compounds comprises the step of reacting a processed lithium hydride reactant with a trisubstituted borane wherein the reaction is maintained for a period of time in a temperature range of approximately 15° C. to approximately 42° C. A method of synthesizing LiH comprises the step of reacting an alkyl lithium (for example, n-butyl lithium) with hydrogen in the presence of tetrahydrofuran. The reaction temperature is preferably maintained in the range of approximately −78° C. to approximately 25° C.
Type:
Grant
Filed:
January 24, 2000
Date of Patent:
April 24, 2001
Assignee:
Mine Safety Appliances Company
Inventors:
Elizabeth R. Burkhardt, Christopher P. Sutton, Joerg Bruening, David F. Rouda
Abstract: A method for synthesizing an alkali-metal amide comprises the step of charging a reactor vessel with a reaction mixture comprising an alkali metal selected from the group of lithium, sodium, potassium or cesium, an electron carrier, and a disubstituted amine. The disubstituted amine preferably has the formula R1R2NH, wherein R1 and R2 are independently, the same or different, an alkyl group or —SiR3, wherein R3 is an alkyl group, an aryl group, or an aryl group substituted with an alkyl group. The reaction to form the alkali-metal amide product occurs without the use of a solvent.
Abstract: The present invention relates to a programmable current or voltage sensing circuit for use in measuring concentration levels of combustible gases. Generally, the present invention provides an electrical apparatus for detecting the concentration level of a combustible gas comprising a pair of sensor elements each having an electrical output which is compared to the other for measuring the amount of the gas undergoing combustion. The apparatus also generally comprises a first pair of electrical circuits each connected to one sensor element for controlling the amount of electrical current or voltage at that element, a second electrical circuit connected to both elements for comparing the electrical outputs of the sensor elements to measure the amount of gas undergoing combustion, and a third electrical circuit having a reference output signal for individually controlling the amount of electrical current or voltage generated by each of the first electrical circuits.