as the solvent and in the presence of a tertiary amine the trimethylchlorosilane/sodium iodide (trimethyliodosilane “in situ”) reagent provides the corresponding siloxy dienes when reacted with α,β-unsaturated series. These reactions occurs via the formation of 1,2 or -1,4 onium salt intermediates.
(1b) and (Z)-buta-1,3-dien-1-yl nonaflate (2) in good yields. The required enolates were obtained by aldehyde-free routes by the lithiation of tetrahydrofuran or 2,5-dihydrofuran followed by the cyclofragmentation of the metallated heterocycles. The application of this approach to the synthesis of allenyl nonaflate 3 failed, presumably due to the intrinsic instability of this allene derivative. The nonaflates
Sigmatropic Reactions in Carbanions. I. The 5, 6-dihydro-2H-pyran-2-ide cyclopropyl-enolate rearrangement
作者:V. Rautenstrauch
DOI:10.1002/hlca.19720550232
日期:1972.1.31
of 5,6-dihydro-2H-pyran (7) gives a mixture of dihydropyranyllithiums 14 and 2. 14 rearranges to 2, and 2 in turn undergoes a [1,4] sigmatropic shift to give the lithium cyclopropyl-enolate 3. Lithiation of nerol oxide 6 gives the lithio derivative 24, which likewise undergoes [1,4] shifts to give cyclopropyl-enolates 28 and 29.
The reactivity and the regioselectivefunctionalization of silyl-diene enol ethers under a bifunctional organocatalyst provokes a dramatic change in the regioselectivity, from the 1,5- to the 1,3-functionalization. This variation makes possible the 1,3-addition of silyl-dienol ethers to nitroalkenes, giving access to the synthesis of tri- and tetrasubstituted double bonds in Rauhut-Currier type products