α-Oxohydrazones as imine component in the synthesis of 4-functionalized azetidinones by the Staudinger reaction
作者:Lara Bianchi、Carlo Dell'Erba、Massimo Maccagno、Angelo Mugnoli、Marino Novi、Giovanni Petrillo、Fernando Sancassan、Cinzia Tavani
DOI:10.1016/j.tet.2003.10.072
日期:2003.12
1-(Methyl-p-tolyl-amino)-3-phenoxy-2-azetidinones 4-COX and 4-R substituted (COX: X=Me, Et, Ph, NMe2, NEt2, OBu'; R=Me, Et, Ph) were smoothly prepared from the corresponding alpha-(methyl-p-tolyl)hydrazonylated ketones, amides and esters via [2+2] cycloaddition with phenoxyketene. The reaction was generally high-yielding and diastereoselective, leading to beta-lactams with a cis relationship between the PhO and the COX moieties, except for R=Ph, where an opposite stereoselectivity was instead observed. The azetidinones represent interesting intermediates which couple protection at N(1) and functionalization at position 4 of the ring. Deprotection of N(1) can be easily attained by oxidative N-N cleavage with magnesium monoperoxyphthalate. (C) 2003 Elsevier Ltd. All rights reserved.