A Formal [3+3] Annulation of Morita–Baylis–Hillman Ketones to Construct Pyrimidobenzothiazoles

Dedicated to Prof. H. Ila on the occasion of her 80^th birthday

Abstract

A calcium triflate-promoted reaction of Morita–Baylis–Hillman (MBH) ketones, derived by the oxidation of MBH adducts, with 2-aminobenzothiazoles resulted in the formation of 4H-pyrimido[2,1-b]benzothiazoles. Formally, the transformation represents a [3+3] annulation and presumably proceeds via an aza-Michael addition followed by an intramolecular condensation. The reaction is completely regioselective and tolerates a wide range of substrates to afford a variety of analogues of the fused heterocycle in good yields.

Key words

Morita–Baylis–Hillman reaction - pyrimidobenzothiazole - [3+3] annulation - MBH ketone - 2-aminobenzothiazole

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