... [Traduit par le journal] ... Acknowledgement We acknowledge financial support for this research from NSERC, Ottawa, Canada. 1. D. SEEBACH and H. 0 . KALINOWSKI. Nachr. Chem. Tech. ... 425-427; (e) AMT FINCH and W. R. VAUCHAN. J. Am. Chem. Soc. 91, 1416 (1969). ...