Sulfoxides as Stereochemical Controllers in Intermolecular Heck Reactions

The study of a variety of substituted sulfoxides as chiral auxiliaries in intermolecular Heck reactions of sulfinyldihydrofurans and sulfinylcyclopentenes with different iodoarenes is reported. In the presence of [Pd(OAc)2]/Ag2CO3 and a bidentate phosphine ligand, synthetically useful yields and asymmetric inductions were obtained. By far the best diastereoselectivities were obtained by the use of the palladium‐coordinating o‐(N,N‐dimethylamino)phenylsulfinyl group. By final removal of the chiral auxiliary, these sulfoxide‐stereocontrolled asymmetric Heck processes were applied to the enantioselective synthesis of 1‐aryl‐substituted and 1,3‐diaryl‐substituted dihydrofurans and cyclopentenes. Se ha abordado el estudio de una amplia variedad de sulfóxidos como auxiliares quirales en reacciones de Heck intermoleculares de sulfinildihidrofuranos y sulfinilciclopentenos con yodoarenos. Elevados rendimientos e inducciones asimétricas apreciables se obtuvieron utilizando [Pd(OAc)2] como catalizador, Ag2CO3 como base y una fosfina bidentada como ligando. Con gran diferencia, las mejores diastereoselectividades se obtuvieron utilizando un sulfóxido con capacidad para coordinarse con el átomo de paladio: el grupo o‐(N,N‐dimetilamino)fenilsulfinilo. Tras eliminación final del auxiliar quiral, estas reacciones de Heck asimétricas controladas por el grupo sulfinilo se han aplicado a la síntesis enantioselectiva de dihidrofuranos y ciclopentenos 1‐aril y 1,3‐diarilsustituidos. The use of the sulfinyl group as a chiral auxiliary in intermolecular Heck reactions of cyclic alkenes with iodoarenes has been studied (see scheme). High asymmetric inductions were obtained by use of the palladium‐chelating o‐(N,N‐dimethylamino)phenylsulfinyl group. Both Heck and double Heck reactions can be performed with this chiral auxiliary. The final reductive elimination of the sulfoxide gave 1‐aryl‐substituted or 1,3‐diaryl‐substituted cyclic compounds in high enantiomeric purity.