The Reaction of Dialkyl Carbonates with o-Aminophenol Catalysed by K₂CO₃: A Novel High-Yield Synthesis of N-Alkylbenzoxazol-2-ones

Abstract

At 130-150 °C and in the presence of catalytic K₂CO₃, o-aminophenol (1) readily reacts with dialkyl carbonates (2: ROCO₂R; 2a: R = Me, 2b: Et, 2c: Allyl, 2d: Bn) to give the corresponding N-alkylbenzoxazol-2-ones (3a-d) in high yields (88-98%). This reaction is a rare example where dialkyl carbonates may simultaneously act as carbonylating and alkylating agents likely through a B_Ac2/B_Al2 sequence. Moreover, compounds 2a-c serve also as solvents. In the case of 2d, 1,2-dimethoxyethane (DME) is the reaction medium.

Key words

alkylations - allylations - benzylations - carbonylations - catalysis

References

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6

The alkylation reaction with 2 takes place only at a high temperature [≥ 120 °C; Scheme [2] , path (a)]. Under these conditions, the alkylation is the sole possible process because of the reversibility of path (b).