α,α-Diisopropylhomoallylic alcohols react with tin(II) chloride and NCS in CH2Cl2 at -40 °C to -60 °C to produce allylic tins and diisopropyl ketone, and the allylic tins in situ cause nucleophilic addition to aldehydes to afford α-substituted homoallylic alcohols.
2-Propenyl tin species, prepared from 3-halopropenes or 2-propenyl mesylate with tin(IV) chloride and tetrabutylammoniumiodide in dichloromethane, causes nucleophilic addition to aldehydes to produce the corresponding homoallylic alcohols.
diastereoselective. The allylation of benzaldehyde by 1-chlorobut-2-ene in 1,3-dimethylimidazolidin-2-one (DMI) does not occur with tin(II) chloride or bromide but does proceed with tin(II) iodide and exhibits gamma-syn selectivity which is unusual for a Barbier-type carbonylallylation. In the carbonylallylation by 1-chlorobut-2-ene with any tin(II) halide, the addition of tetrabutylammoniumiodide (TBAI) accelerates
Gallium-Mediated Allyl Transfer from Bulky Homoallylic Alcohol to Aldehydes via Retro-allylation: Stereoselective Synthesis of Both <i>e</i><i>rythro</i>- and <i>t</i><i>hreo</i>-Homoallylic Alcohols<sup>1</sup>
Retro-allylation of bulky gallium homoallylic alkoxides occurs to generate (Z)- and (E)-crotylgallium reagents stereospecifically, starting from erythro- and threo-homoallylic alcohols, respectively. The (Z)- and (E)-crotylgallium reagents immediately reacted with aromatic aldehydes to afford the corresponding erythro- and threo-homoallylic alcohols, respectively. [reaction: see text]
(E)-rich 1-Bromo-2-butene preferentially caused γ-syn-allylation of aldehydes with tin(II) iodide and tetrabutylammoniumbromide (or iodide) in THF-H2O or 1,3-dimethyl-2-imidazolidinone-H2O to produce 1-substituted syn-2-methyl-3-buten-1-ols.