The application of intramolecular radical cyclizations of acylsilanes in the regiospecific formation of cyclic silyl enol ethers
The application of intramolecular radical cyclizations of acylsilanes in the regiospecific formation of cyclic silyl enol ethers
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DOI：
10.1021/jo010883s
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发表时间：
2001-12-28
影响因子：
3.6
通讯作者：
Tsai, YM
中科院分区：
文献类型：
--
作者：
Huang, CH;Chang, SY;Tsai, YM
制备具有末端α-甲锡烷基溴化物或黄原酸酯官能团的酰基硅烷。由这些酰基硅烷产生的α-甲锡烷基自由基经历分子内环化以区域特异性地产生环状甲硅烷基烯醇醚。自由基过程依次包括自由基环化、布鲁克重排和β-断裂。三丁基甲锡烷基用作自由基离去基团。新形成的σ键和π键位于相同的两个碳原子之间。这种方法仅限于五元环的形成。在另一条路线中，合成了omega-溴-α-苯磺酰酰基硅烷。这些α-磺酰酰基硅烷的自由基环化也产生环状甲硅烷基烯醇醚。苯磺酰基部分是该系统中的自由基离去基团。此外，新形成的σ键和π键位于共享单个碳原子的相邻位置。后一种方法对于五元环和六元环的形成均有效。
Acylsilanes with terminal alpha -stannyl bromide or xanthate functionalities are prepared. alpha -Stannyl radicals generated from these acylsilanes undergo intramolecular cyclizations to give cyclic silyl enol ethers regiospecifically. The radical processes involve radical cyclization, Brook rearrangement, and beta -fragmentation in sequence. A tributylstannyl group serves as the radical leaving group. The newly formed sigma -bond and pi -bond are located between the same two carbon atoms. This approach is limited to the formation of five-membered rings. In another route, omega -bromo-alpha -phenylsulfonylacylsilanes are synthesized. The radical cyclizations of these alpha -sulfonylacylsilanes also give cyclic silyl enol ethers. The phenylsulfonyl moiety is the radical leaving group in this system. Furthermore, the newly formed sigma -bond and pi -bond are located at adjacent positions sharing a single carbon atom. The latter approach is effective for both five- and six-membered ring formation.