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Surpassing Torquoelectronic Effects in Conrotatory Ring Closures: Origins of Stereocontrol in Intramolecular Ketenimine–Imine [2+2] Cycloadditions
Author(s) -
Alajarín Mateo,
Vidal Angel,
Tovar Fulgencio,
Arrieta Ana,
Lecea Begoña,
Cossío Fernando P.
Publication year - 1999
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/(sici)1521-3765(19990301)5:3<1106::aid-chem1106>3.0.co;2-i
Subject(s) - conrotatory and disrotatory , ketenimine , intramolecular force , imine , chemistry , ring (chemistry) , methylene , nitrogen atom , ab initio , stereochemistry , computational chemistry , medicinal chemistry , organic chemistry , catalysis
Unexpected and almost perfect stereochemical control is obtained in the title reactions [Eq. (a)], although torquoelectronic theory predicts negligible stereoselection. According to ab initio and DFT calculations, this stereocontrol is determined by the geometry of the first transition state of the stepwise mechanism. In good agreement with the model proposed, the presence of an additional methylene group attached to the iminic nitrogen atom promotes a significant loss of stereocontrol.