Pub No:
308
Title:
Nucleophilic Reaction of 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diaza-bicyclo[4.3.0]non-5-ene with Methyl Pheophorbide a. Unexpected Products
Authors:
Ma, L. and David Dolphin
Journal:
Tetrahedron Lett.
Year:
1996
Pages:
52(3), 849-860
Abstract:
Trialkylsilyl triflates promote the direct nucleophilic reaction of “non-nucleophilic DBU and DBN” with methyl pheophorbide a to give substituted chlorin e6 amides, where the bicyclic bases have undergone ring opening. The reaction most likely results from coordination of trialkylsilyl triflates to the β-ketoester, forming an ion-pair intermediate. The adduct is so strongly electron-deficient that it can electrophilically attack the nonbonding nitrogen electron pairs in DBU and DBN.

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