Structural Insight Into Oxybenzotriazole Based Coupling Reagents

Present work encompasses a detailed solution and solid phase NMR spectroscopic studies on oxybenzotriazole based coupling reagents namely HBTU (1), NBTU (2) and BOP (3). The present finding unequivocally establish that the correct structure of oxybenzotriazole based coupling reagents both in the solution and solid states are benzotriazolyl N-oxides as shown in 1a, 2a and 3a and not the uronium form as represented in the current literature.