piperidines has been researched along with tris(trimethylsilyl)silane* in 2 studies
2 other study(ies) available for piperidines and tris(trimethylsilyl)silane
| Article | Year |
|---|---|
Synthesis of 2,4-disubstituted piperidines via radical cyclization: unexpected enhancement in diastereoselectivity with tris(trimethylsilyl)silane.
A novel approach to 2,4-disubstituted piperidines is reported, involving the radical cyclization of 7-substituted-6-aza-8-bromooct-2-enoates. Cyclization with tributyltin hydride affords the trans piperidines with trans/cis diastereomeric ratios ranging typically from 3:1 to 6:1. Cyclization with tris(trimethylsilyl)silane affords the same products with diastereomeric ratios of up to 99:1 in certain cases. The enhancement in diastereoselectivity results from the selective rearrangement of the minor stereoisomer through a cascade process involving radical cyclization to the piperidine radical, 1,5-radical translocation, and attack of the translocated radical onto the sulfonamide with extrusion of SO2 in a Smiles-type rearrangement. Slower trapping of the piperidine radical by tris(trimethylsilyl)silane compared to tributyltin hydride accounts for the occurrence of the rearrangement cascade in the former case. Topics: Cyclization; Free Radicals; Molecular Structure; Piperidines; Silanes; Stereoisomerism | 2006 |
Tris(trimethylsilyl)silane: an unprecedented enhancement in the diastereoselectivity of radical cyclisations to give 2,4-disubstituted piperidines.
Cyclisation of bromides 4a-f mediated by tributyltin hydride affords predominantly the trans piperidines 5a-f with modest diastereomeric ratios, while cyclisation with tris(trimethylsilyl)silane affords the same products with diastereomeric ratios of up to 99 : 1. Topics: Cyclization; Free Radicals; Molecular Structure; Piperidines; Silanes; Stereoisomerism | 2004 |