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Application of the Octacarbonyldicobalt‐Catalyzed Carbonylation of Ethyl Diazoacetate for the One‐Pot Synthesis of N ‐ tert ‐Butyl‐ trans ‐α‐ethoxycarbonyl‐β‐phenyl‐β‐lactam
Author(s) -
Fördős Eszter,
Tuba Róbert,
Párkányi László,
Kégl Tamás,
Ungváry Ferenc
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200801247
Subject(s) - chemistry , carbonylation , catalysis , ethyl diazoacetate , dichloromethane , ketene , medicinal chemistry , carbon monoxide , cycloaddition , imine , lactam , stereochemistry , organic chemistry , cyclopropanation , solvent
N ‐ tert ‐Butyl‐ trans ‐α‐ethoxycarbonyl‐β‐phenyl‐β‐lactam has been prepared in 95 % yield (GC) by the octacarbonyldicobalt‐catalyzed carbonylation of ethyl diazoacetate in dichloromethane in the presence of N ‐ tert ‐butylbenzaldimine at 10 °C and 75 bar pressure of carbon monoxide. The key step of the reaction is the catalytic formation of the highly reactive (ethoxycarbonyl)ketene from both of the intermediary complexes [Co 2 (CO) 7 (CHCO 2 Et)] and [Co 2 (CO) 6 (CHCO 2 Et) 2 ], which is in situ scavenged by the imine in a [2+2] cycloaddition reaction. DFT (PBEPBE/6‐31G**) calculations revealed that the reaction follows a two‐step mechanism via a noncyclic intermediate with a reaction free energy of –15.9 kcal/mol and a free‐energy barrier of 24.7 kcal/mol for the second rate‐limiting step. The computation also shows that the formation of the trans isomer is preferred both kinetically and thermodynamically. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)