Construction of Quaternary Stereogenic Centers via [2 + 2] Cycloaddition Reactions. Synthesis of Homochiral 4,4-Disubstituted 2-Azetidinones and Imine Substituent Effects on β-Lactam Formation

Autor:	Regina Galarza, Anthony Linden, Antonio Luque, Claudio Palomo, Marta Legido, Jesus M. Aizpurua, R. Urchegui, † Juan Server-Carrió, Pascual Román, Jesús M. García
Rok vydání:	1997
Předmět:	chemistry.chemical_compound Trimethylsilyl chemistry Stereochemistry Organic Chemistry Imine Enantioselective synthesis Lactam Ketene Asymmetric induction Cycloaddition Stereocenter
Zdroj:	The Journal of Organic Chemistry. 62:2070-2079
ISSN:	1520-6904 0022-3263
DOI:	10.1021/jo962017z
Popis:	A study on the asymmetric construction of quaternary stereogenic centers via [2 + 2] cycloaddition reaction of ketenes with ketimines is described. Reaction of achiral ketenes and chiral alpha-alkoxy ketone-derived imines resulted in formation of new beta-lactams as single diastereomers. The cycloaddition was extended to pyruvate imines, aralkyl ketone-derived imines, and dialkyl ketimines. In these cases the asymmetric induction was satisfactorily achieved using beta-silylalkanoyl ketenes and the Evans-Sjögren ketene. C,C-Bis (trimethylsilyl)methylamine ketimines derived from enolizable dialkyl ketones cleanly led to the corresponding C(4) disubstituted beta-lactams without deprotonation. Therefore, a general methodology for a convergent asymmetric synthesis of beta-lactams in which C(4) exists as a quaternary carbon is provided.
Databáze:	OpenAIRE
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