Synthesis of Novel Functionalised Symmetric Bi-2(1H)-pyrazinones

Abstract

A simple and convenient synthesis for functionalised bi-2(1H)-pyrazinones 9, 11a-h starting from 3,5-dichloro-2(1H)-pyrazinones 7, 10a-h is described. The pyrazinone is homo-coupled by means of a Suzuki-type reaction of an in situ generated boronate. The reactions were carried out under conventional heating as well as under microwave irradiation and dramatic improvements in the rates and yields have been observed under the latter conditions.

bis-heterocycle - pyrazinone - Suzuki chemistry - bis(pinacolato)diboron

References

<A NAME="RD33304ST-1">1</A>

Currently on a leave of absence from Helwan University, Cairo, Egypt.

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We tried to suppress the homodimerisation by slowly adding a solution of pyrazinone 10b (1 mmol in 10 mL of dioxane) via an infusion pump (over a time period of 3 h) to a stirred suspension of [B(Pin)]₂ (1 mmol), K₂CO₃ (1 mmol) and tetrakis (3 mol%) in 10 mL of dioxane at 80 °C. However, even using slow addition, the formation of the bipyrazinones could not be prevented.

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EM-Discover, CEM Corporation P.O. Box 200 Matthews, NC 28106.

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Also in the microwave experiments, formation of minor amounts of protodeboronation product (<10%) could not be avoided.