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Pyridine‐Catalyzed Stereoselective Addition of Acyclic 1,2‐Diones to Acetylenic Esters: Synthetic and Theoretical Studies of an Unprecedented Rearrangement
Author(s) -
Pillai Abhilash N.,
Suresh Cherumuttathu H.,
Nair Vijay
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800250
Subject(s) - chemistry , pyridine , stereoselectivity , catalysis , zwitterion , acetylene , medicinal chemistry , organic chemistry , molecule
A systematic study of the addition of various 1,2‐acyclic diones to activated acetylenic esters catalyzed by pyridine under mild conditions is described. This reaction provides a new protocol for the stereoselective synthesis of 1,2‐diaroyl maleates. The exclusive formation of the cis isomer is especially noteworthy. This reaction occurs through the initial generation of a pyridine–dimethyl acetylene dicarboxylate zwitterion and its addition to the dione followed by an unprecedented benzoyl migration. Pyridine and substituted pyridines, such as 4‐dimethylaminopyridine (DMAP) and 3‐methoxypyridine, are the best catalysts and anhydrous 1,2‐dimethoxyethane is found to be the solvent of choice. Structural, electronic, energetic and mechanistic details of the reaction are also revealed by density functional theory calculations, which strongly support the exclusive formation of the cis isomer of the 1,2‐diaroyl maleates.