Rapid and Stereocontrolled Synthesis of Racemic and Optically Pure Highly Functionalized Pyrrolizidine Systems via Rearrangement of 1,3-Dipolar Cycloadducts Derived from 2-Azetidinone-Tethered Azomethine Ylides
作者:Benito Alcaide、Pedro Almendros、Jose M. Alonso、Moustafa F. Aly
DOI:10.1021/jo005686s
日期:2001.2.1
a convenient procedure for the straightforward preparation of polyfunctionalized enantiopure pyrrolizidine systems. The methodology capitalizes on a HCl(g)-promoted reaction of the 1,3-dipolar cycloadducts derived from 2-azetidinone-tethered azomethine ylides, smoothly affording different types of highly functionalized bi- and tricyclic systems in racemic and optically pure forms. This process involves
1,3-Dipolar cycloaddition of 2-azetidinone-tethered azomethine ylides. Application to the rapid, stereocontrolled synthesis of optically pure highly functionalised pyrrolizidine systems
作者:Benito Alcaide、Pedro Almendros、Jose M. Alonso、Moustafa F. Aly
DOI:10.1039/b000249f
日期:——
A new straightforward methodology to prepare
polyfunctionalised enantiopure pyrrolizidine systems, based on the
1,3-dipolar cycloaddition of 2-azetidinone-tethered azomethine ylides as
the key reaction, is presented.
Synthesis of Strained Tricyclic β-Lactams by Intramolecular [2+2] Cycloaddition Reactions of 2-Azetidinone-Tethered Enallenols: Control of Regioselectivity by Selective Alkene Substitution
作者:Benito Alcaide、Pedro Almendros、Cristina Aragoncillo、María C. Redondo、M. Rosario Torres
DOI:10.1002/chem.200500807
日期:2006.2.1
preparation of structurally novel, strained tricyclic beta-lactams containing a cyclobutane ring has been developed. The first examples accounting for the intramolecular [2+2] cycloaddition reactions in beta-lactams have been achieved by the thermolysis of 2-azetidinone-tethered enallenols, which have been prepared in aqueous media by regio- and diastereoselective indium-mediated carbonyl allenylation of 4-
Metal-mediated carbonyl allenylation and propargylation of 4-oxoazetidine-2-carbaldehydes were investigated in aqueous environment. Different propargyl bromide and metal promoters showed varied regio- and stereoselectivities on product formation. In addition, an unprecedented one-pot stereoselective synthesis of beta-chlorinated allylic alcohols, which can also be considered as functionalized allylsilanes
Reactions of racemic as well as optically pure carbonyl-β-lactams with stabilized organo-indium reagents were investigated in aqueous media. The regio- and stereochemistry of the processes were generally good, offering a convenient asymmetric entry to densely functionalized hydroxy-β-lactams.