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First Use of Axially Chiral Thioamides for the Stereocontrol of C−C Bond Formation
Author(s) -
Dantale Shubhada,
Reboul Vincent,
Metzner Patrick,
Philouze Christian
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020201)8:3<632::aid-chem632>3.0.co;2-x
Subject(s) - thioamide , chemistry , aryl , diastereomer , chirality (physics) , stereochemistry , deprotonation , conformational isomerism , axial chirality , medicinal chemistry , molecule , organic chemistry , ion , catalysis , enantioselective synthesis , alkyl , chiral symmetry breaking , physics , quantum mechanics , nambu–jona lasinio model , quark
Several N ‐aryl‐substituted thioamides with an axis of chirality along the N−C(aryl) bond were prepared in good to excellent yields. NMR spectra revealed preferences for the E rotamer (along the N−C(=S) bond). X‐ray crystallographic analysis showed that the planes of the aryl and thioamide groups were almost perpendicular (79°). For the first time, these atropisomeric thioamides were used for an asymmetric Claisen rearrangement. LDA deprotonation led selectively to the enethiolates of Z stereochemistry, and subsequent reaction with a variety of allyl halides furnished S ‐allyl keteneaminothioacetals. These intermediates were not detected as they rearranged readily to γ ‐unsaturated thioamides in good to high yields and diastereoselectivities up to 88:12. Chemical correlation allowed the assignment of the (a R *,2 R *) configuration to the major diastereoisomer. A model was proposed to explain the stereochemical course of the thio‐Claisen rearrangement.