The unidirectional thermal ring-closing reaction of cis-4-phenyl-5-borylpenta-1,2,4-triene giving 4-boryl-3-methylene-1-phenylcyclobutene proceeded significantly faster than that of the trans-isomer. The large rate difference between the cis- and trans-stereoisomers is ascribed to electronic participation of the vacant boron p orbital in the transition state SHOMO.
顺式-4-苯基-5-borylpenta-1,2,4-triene 产生 4-boryl-3-methylene-1-phenylcyclobutene 的单向热闭环反应比反式异构体进行得快得多。顺式和反式立体异构体之间的巨大速率差异归因于过渡态 SHOMO 中空硼 p 轨道的电子参与。
NOTH, H.;SCHWERTHOFFER, R., CHEM. BER., 1981, 114, N 9, 3056-3062