Visible‐Light‐Induced Cycloaddition of α‐Ketoacylsilanes with Imines: Facile Access to β‐Lactams
作者:Jian‐Heng Ye、Peter Bellotti、Tiffany O. Paulisch、Constantin G. Daniliuc、Frank Glorius
DOI:10.1002/anie.202102451
日期:2021.6.7
report the synthesis of β-lactams from α-ketoacylsilanes and imines, which proceeds via a formal [2+2] photochemical cycloaddition with in situ generation of siloxyketene. This mild and operationally simple reaction proceeds in an atom-economic fashion with broad substrate scope, including aldimines, ketimines, hydrazones, and fused nitrogen heterocycles, affording a variety of important β-lactams with satisfactory
Seebach's synthetic method of self-regeneration of stereocenters ''SRS'' has been applied to the addition reaction of diphenylimine 1 to the lithium enolates of (2S,5S)-2-(tert-butyl)-5-methyl-1,3-dioxolan-4-one 2a and of (2S,5S)-2-(tert-butyl)-5-phenyl-1,3-dioxolan-4-one 2b. Variable 4S/4R mixtures of (3R)-S-hydroxy-beta-lactams 4a,b are obtained, depending on the reaction conditions. The induced enantioselectivity (ee) is very high, and the simple selectivity (exo-endo) is low. Overall, this appears a rather direct approach to chiral beta-lactams with full control of stereochemistry at C3. The stereoselective radical reduction of the stereoisomer (3R,4R)-E-4a afforded the homochiral C3,C4-monosubstituted beta-lactam (3S,4S)-Z-10. (C) 1997 Elsevier Science Ltd.
Assessment of the absolute configuration of a series of (3R)-3-hydroxy-3-alkyl-β-lactams
The absolute stereochemistry of a series of (3R)-3-hydroxy-3-alkyl-beta-lactams has been determined by circular dichroism and NMR spectroscopies. The sign of the circular dichroism band between 250 and 220 nm was related to the stereochemistry by applying the beta-lactam sector rule. The NMR analysis unambiguously determines the relative configuration at C3 and C4 of the beta-lactam ring. The reliability of the method has been proved by X-ray analysis of two of the examined compounds. The obtained results are in agreement with the mechanism proposed for the employed synthetic route. (C) 1998 Elsevier Science Ltd. All rights reserved.
GLUCHOWSKI C.; COOPER L.; BERGBREITER D. E.; NEWCOMB M., J. ORG. CHEM., 1980, 45, NO 17, 3413-3416
作者:GLUCHOWSKI C.、 COOPER L.、 BERGBREITER D. E.、 NEWCOMB M.