Stereoselective Functionalization of Alkenyl-b-Lactams.

Alkenyl-β-lactams, obtained by palladium-catalyzed [2+2] cycloaddition of imines with allyl halides, were functionalized in a stereoselective way by a simple deprotonation with LDA, and subsequent capture of the formed carbanion by various electrophiles. Alkyl, hydroxy and epoxy functionalities were inserted exclusively at the C-3 carbon atom of the β-lactamic system, without performing new cyclizations. High stereoselectivity was noticed with the quenching taking place preferentially at the Cα with respect to the Cγ carbon atom of the allylic moiety of the azetidinyl anion generated by deprotonation

Synthesis and isomerization of N-alpha-aza-heteroaryl-beta-lactams

The [2+2] carbonylative cycloaddition of N-cx-aza-heteroaryl substituted imines with allyl bromide led partially to beta-lactams, which underwent isomerization to the more stable alpha,beta-unsaturated carbonyl compound. Pyrimidinone derivatives together with doubly unsaturated amides represent the remaining isolated products. The strong electron-withdrawing effect of the two alpha-aza-heterocycles linked to the nitrogen atom and to the C4 of the 2-azetidinone structure could give a ring expansion, through a 2-azetinone intermediate that affords the pyrimidinone compounds. The substituted amides, instead, should result from a ring-opening reaction of the beta-lactam. (c) 2006 Elsevier Ltd. All rights reserved

Stereoselective synthesis of 2-acyl-3,4-dihydro-1,4-benzothiazines

2-Benzylidene-4-methyl-3-oxo-2H-1,4-benzothiazine 2 undergoes 1,2-addition with MeMgI and allylic magnesium halides to give 2-acyl-4-methyl-3-phenyl-3,4-dihydro-2H-1,4-benzothiazines 3a-d. Lithiation of 3a and subsequent reaction with MeI and PhCH2Br leads to compounds 3e, 3f, 3h and 3i. In contrast, the reaction of lithiated 3a with benzaldehyde and 2,6-dichlorobenzaldehyde furnished compounds 3k and 3l respectively. © 1994

Stereoselective Synthesis of Heterosubstituted Aziridines and Their Functionalization.

Lithiated (alfa-chloroalkyl)heterocycles, generated by deprotonation with LDA at -78 °C in THF, add to various enantiopure imines affording ‘one pot’ chiral heterosubstituted aziridines in a diastereoselective manner. Lithiated heterosubstituted aziridines, obtained by deprotonation of the corresponding aziridines with n-BuLi at -78 °C in THF, were trapped by electrophiles (D2O or CH3I) with high stereoselectivity