Enantioselective allylboration of aldehydes with α-substituted β-methyl allylboronate was reported. By using BF₃·OEt₂ as the catalyst, γ,δ-disubstituted homoallylic alcohols were obtained in good yields with high E-selectivities and enantioselectivities. Transition state analysis revealed that the disfavored transition state suffers from a syn-pentane interaction between the BF₃ catalyst and axially oriented α-substituent of the allylboron reagent. Such a syn-pentane interaction is severe enough to overcome the A^1,2 allylic strain between the β-methyl group and the α-substituent of the boron reagent that is present in the favored competing transition state. Consequently, the reaction proceeded with equatorial placement of the α-substituent to furnish γ-methyl substituted homoallylic alcohols with high E-selectivity.

报道了醛与α-取代的β-甲基烯丙基硼酸酯的对映选择性烯丙基硼化。以BF ₃ ·OEt ₂为催化剂，可以得到高产率，高E选择性和对映选择性的γ，δ-二取代均烯丙基醇。过渡状态分析表明，从该不受欢迎过渡状态患有顺式的BF之间戊烷相互作用₃催化剂和allylboron试剂的轴向定向的α取代基。这样的顺式-戊烷相互作用是严重足以克服甲^1,2-以有利的竞争过渡态存在的硼试剂的β-甲基和α-取代基之间的烯丙基应变。因此，该反应在赤道放置α-取代基的情况下进行，以提供具有高E-选择性的γ-甲基取代的均烯丙基醇。