Allylic alcohols were readily converted into allylic iodides by hydrogen iodide generated in situ from chlorotrimethylsilane/sodium iodide and water, or alcohols, under mild conditions. Displacement of allylic alcohols containing a terminal double bond gave allylic iodides accompanied by allylic rearrangement. This procedure has successfully been extended to a one-pot synthesis of homoallylic alcohols by carrying out successive Barbier type reactions.
The reaction of crotyltrialkylstannanes (1) with aldehydes in the presence of BF3,OEt2, produces the corresponding erythro homoallyl alcohols (2) predominantly regardless of the geometry of the double bond. Further, the Lewis acid mediated reaction exhibits the enhanced Cram selectivity in comparison with other allylic organometallic reactions which proceed in the absence of Lewis acids. Use of AlCl3-i-PrOH
Boronates allyliques, alleniques et propargyliques: Preparations et proprietes
作者:J Blais、A L'Honore、J Soulie、P Cadiot
DOI:10.1016/s0022-328x(00)80482-9
日期:1974.10
An easy synthesis of linear cyclic 2-unsaturated boronates via organometallic reagents has been achieved. The final structure of the carbon framework is related to the tetracoordinated intermediate. Intermolecular rearrangement, disproportionation and reactions with carbonyl compounds have been studied.
The reaction of but-2-enyltributylstannane with certain aldehydes in the presence of AlCl3–PriOH produces the α-adduct (3) either predominantly or exclusively, while the reaction in the presence of ordinary Lewis acids, such as TiCl4, SnCl4, and BF3·OEt2, affords the γ-adduct (2) exclusively.
Chemistry of organosilicon compounds 113 chemoselective allylation of carbonyl compounds with allylsilanes promoted by tetra--butylammonium fluoride. A new synthesis of homoallyl alcohols