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Mechanism of Anionic Dearomatizing Reactions of Diphenylphosphinamide Derivatives: A Theoretical and Experimental Study
Author(s) -
Ramallal Antonio Morán,
Fernández Ignacio,
López Ortiz Fernando,
González Javier
Publication year - 2006
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.200400987
Subject(s) - mechanism (biology) , chemistry , computational chemistry , epistemology , philosophy
The mechanism of the anionic dearomatisation of phosphinamide derivatives has been investigated both theoretically and experimentally. The potential‐energy surface of model reactions was studied at the Becke3LYP/6‐31+G* level of theory, and according to this study, a pre‐reactive complex is formed between the alkyllithium and the phosphinamide. This complex evolves preferentially through NC α ‐metalation of the phosphinamide. The intramolecular nucleophilic addition of the carbanion to the ortho position of the aromatic ring leads to the dearomatised products, in a reaction that has been shown to be under thermodynamic control. Coordinating co‐solvents, such as hexamethyl phosphoramide (HMPA) or N , N ′‐dimethyl‐ N , N ′‐propylene urea (DMPU), appear to influence the reaction by favouring the formation of solvent‐separated ion pairs. The cyclisation reaction of allylphosphinamide derivatives was also studied. It was found that both the α‐ and γ‐attack of the allyl anion can take place, however the formation of the seven‐membered ring products derived from the γ‐attack are clearly favoured.