Nitrogen hydrides silyl derivatives

Yttrium-catalyzed diene cyclization/hydrosilylation was applied to the synthesis of aliphatic nitrogen heterocycles such as the indolizidine alkaloid ( )-epilupinine. l-Allyl-2-vinylpiperidine 30 was synthesized in four steps in 59% overall yield from commercially available ( )-2-piperidinemethanol (Scheme 10). Treatment of 30 with phenylsilane and a catalytic amount of Gp 2YGH3(THF) gave silylated quinolizidine derivative 31 in 84% yield, resulting from selective hydrometallation of the A-allyl G=G bond in preference to the exocyclic vinylic G=G bond. Oxidation of the crude reaction mixture with tert-huVf hydrogen peroxide and potassium hydride gave (i)-epilupinine in 51-62% yield from 30 (Scheme 10). 

Deprotonation of Al,<9-bis(trimethylsilyl)hydroxylamine with n-butyllithium or potassium hydride at low temperature yields the nitrogen centered anion Al,<9-bis(trimethylsilyl)hydroxyl-amide. At higher temperatures the oxyanion Al,A -bis(tri-methylsilyl)hydroxylamide is formed by rearrangement. Each reacts with acyl chlorides chemospecifically by M-acylation and 0-acylation, respectively. The oxyanion also reacts with silyl halides, methyl iodide, and sulfonyl chlorides chemospecifically on oxygen. In a Peterson-type one-pot reaction, oximes and oxime derivatives can be prepared effectively from the N-anion of iV,0-bis(trimethylsilyl)hydroxylamine and an aldehyde or ketone (eq 5). Oximes of sterically hindered ketones can be formed in high yields by this procedure. 

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