Jesús H. Rodríguez Ramos

Anchimeric assistance of the sulfinyl group in the hydrolysis of cyano groups: A new mild method for the reduction of sulfoxides

Abstract Conditions to achieve reductive hydrolysis of β-cyanosulfoxides into their corresponding β-sulfenylamides are reported. The anchimeric assistance of the sulfinyl oxygen in the hydrolysis of the cyano group is proposed to explain the mild conditions required to achieve it and several proofs supporting this assumption are indicated. From these results a new mild method to transform sulfoxides into sulfides has been developed.

Stereoselective Hydrocyanation of Alkenyl Sulfoxides as a Method to Highly Enantiomerically Enriched Compounds with Tertiary and Quaternary Chiral Carbon Atoms

Terminal alkynes are easily transformed into enantiomerically enriched compounds containing tertiary and quaternary carbon atoms. Sulfinylation followed by reduction (or alkylation) and hydrocyanation of the resulting vinyl sulfoxides with Et2 AlCN provides nitriles bearing the chiral center, which can in turn undergo reaction to form the desired products. Tol=4-tolyl.

Enantiomerically pure 2-alkyl and 2,3-dialkylaziridines from 2-sulfinylimines

Abstract A new entry to optically pure aziridines from N-p-methoxyphenyl derivatives of 2-p-tolylsulfinylketimines is reported. The highly stereoselective reduction of the imines with DIBAL-H/ZnX2 yielded the corresponding sulfinyl amines, which can be transformed into the N-Cbz derivatives through a two-step sequence involving reaction with BnO2CCl and subsequent oxidation with CAN. These compounds were easily transformed into optically pure aziridines by reduction of the sulfinyl group, further methylation at sulfur, and final cyclization with base.

Synthesis of enantiomerically pure 2,3-disubstituted oxirane-2-carboxamides

Abstract The title compounds were efficiently prepared from 1-alkyl(or phenyl)-2-methyl-2-(tolylsulfinyl)ethanone through a simple four-step sequence: highly stereoselective hydrocyanation with Et 2 AlCN (key step to control the stereochemistry); hydrolysis to sulfinylamides and separation of epimers; reduction of the sulfur functionality; and final cyclization to enantiopure oxirane derivatives.

Highly stereoselective reduction of acyclic α-sulfinyl ketimines: synthesis of enantiomerically pure β-aminosulfoxides

Abstract The DIBAL reduction of enantiomerically pure α-sulfinyl ketimines can be achieved almost completely stereoselectively under ZnX2 catalysis, regardless of the alkyl or aryl substituent at nitrogen and the aliphatic (cyclic or acyclic) or aromatic character of the imine. Steric factors as well as the electrophilic character of the hydride are responsible for the stereochemical course of the reduction.

Synthesis of enantiomerically pure acyclic α-sulfinyl ketimines

Abstract Two different methods to obtain enantiomerically pure N -alkyl and N -aryl α-sulfinyl ketimines are reported. Reaction of enantiomerically pure α-sulfinyl ketones ( 1 – 6 ) with benzylamine or p -methoxyaniline, in the presence of molecular sieves (3 A), yields the corresponding of N -benzyl and N - p -methoxyphenyl ketimines ( 7A – 12A and 7B – 12B ). Better results were achieved by α-sulfinylation of ketimines ( 13A – 18A and 13B – 18B ) with (−)-menthyl p -toluenesulfinate in the presence of lithium ( N -arylimines) or magnesium ( N -benzylimines) bases. The different tautomeric behaviour of the obtained N -aryl and N -alkyl derivatives is reported.

Highly stereoselective hydrocyanation of optically pure α-sulfinylaldehydes

Abstract Diastereoselective hydrocyanation of enantiomerically pure 2- p -tolylsulfinylacetaldehyde and 2- p -tolylsulfinylpropanal with Et 2 AlCN catalyzed by ZnBr 2 is described. The sulfur configuration controls the stereochemical course of the reaction. Hydrolysis of the resulting cyanohydrins and further desulfurization yielded the corresponding α-hydroxyamides in high ees (90%).

Regio- and stereocontrolled hydrocyanation of chiral 2-alkylglycidamides with Et2AlCN: synthesis of enantiomerically pure mono- and disubstituted malic acid derivatives

Abstract The opening of the oxirane ring of glycidamides with Et 2 AlCN takes place under mild conditions in a completely regio- and stereoselective manner to afford β-cyano carboxamide derivatives, which are immediate precursors of mono- and disubstituted malic acid derivatives. The complete control of the regioselectivity can be rationalized as a consequence of the association of the reagent with the carboxamide group prior to intramolecular cyanide transfer.