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Synlett 2005(5): 0777-0780  
DOI: 10.1055/s-2005-863747
LETTER
© Georg Thieme Verlag Stuttgart · New York

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

Wim M. De Borggraeve*a, Prasad Appukkuttana, Rasha Azzamb,, Wim Dehaena, Frans Compernollea, Erik Van der Eyckena, Georges Hoornaerta
a K. U. Leuven, Chemistry Department, Laboratory for Organic Synthesis, Celestijnenlaan 200F, 3001 Leuven, Belgium
b Department of Chemistry, Helwan University, Ain-Helwan, Cairo, 11795, Egypt
Fax: +32(16)327990; e-Mail: Wim.DeBorggraeve@chem.kuleuven.ac.be;
Further Information

Publication History

Received 8 November 2004
Publication Date:
09 March 2005 (online)

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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.

Key words

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

1

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

8

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.

11

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

12

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