Highly Regio- and Stereoselective Allylation of α-Diketones via the Fluorosilicate Route

Rainer Gewald; Mitsuo Kira; Hideki Sakurai

doi:10.1055/s-1996-4151

Synthesis 1996; 1996(1): 111-115
DOI: 10.1055/s-1996-4151

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Highly Regio- and Stereoselective Allylation of α-Diketones via the Fluorosilicate Route

Rainer Gewald^* , Mitsuo Kira, Hideki Sakurai

^*Department of Chemistry and Organosilicon Research Laboratory, Faculty of Science, Tohoku University, Aoba-ku, Sendai 980, Japan

Abstract

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Allylation of enolizable α-diketones with allyltrifluorosilanes in the presence of triethylamine gave the corresponding tertiary homoallyl alcohols in good yield in a highly regio- and stereospecific manner. The reaction proceeds as diallylation with allyltrifluorosilanes yielding the 1,2-diols with high diastereoselectivity. The more sterically demanding crotyl- and prenyltrifluorosilanes lead exclusively to monoallylated products with the allyl group being added γ-regioselectively. In addition, highly diastereoselective crotylation was observed in the formation of the monoallylated α-hydroxy ketones. Asymmetric α-diketones were generally allylated at the less enolized ketone group except when both diketone and allylsilane were sterically hindered.

α-diketones - allyltrifluorosilanes - allylation - regioselectivity - stereoselectivity

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