An investigation of the behaviour of α,β-unsaturated sulfoxides in the presence of trimethylsilyl iodide
摘要:
A mild, efficient and seemingly general method for converting alpha,beta-unsaturated sulfoxides into carbonyl compounds by means of trimethylsilyl iodide (TMSI) is described. Experiments on different substrates and trimethylsilyl halides lead to the conclusion that the oxidation state of the sulfur atom, on one hand, and halogen kind in TMSX on the other, assume a determining role in the progression of the reaction. The ease of experimental procedure, the possibility of H-1 NMR monitoring, and good yields of final products constitute advantages of the TMSI-promoted conversion of alpha,beta-unsaturated sulfoxides into carbonyl compounds. (C) 2002 Elsevier Science Ltd. All rights reserved.
Diels–Alder reactions of (RS)-3-[(1S)-isoborneol-10-sulfinyl]-1-methoxybuta-1,3-dienes with electron-deficient carbodienophiles. The effects of Lewis acid catalysis
摘要:
Uncatalyzed cycloadditions of (R-s,E)-1 and (R-s,2)-3-[(1S)-isoborneol-10-sulfinyl]-1-methoxybuta-1,3-diene 2 with maleimide and N-phenylmaleimide occurred with complete endo and very high facial diastereoselectivities. The effects of Lewis acid catalysis on these Diels-Alder reactions have been evaluated. LiClO4 catalyzed cycloaddition of 1 with dimethyl maleate gave cyclohexene 13 as the unique product with complete control of endo and pi-facial diastereoselectivities exerted by the sulfinyl group. A significant improvement in diastereoselectivity was also observed in the LiClO4 catalyzed cycloaddition of 1 with dimethyl fumarate. (C) 1998 Elsevier Science Ltd. All rights reserved.