title: Novel synthesis of alkenes via triethylborane-induced free-radical reactions of alkyl iodides and beta-nitrostyrenes.
abstract: Reactions of (E)-beta-nitrostyrenes 1 and triethylborane 2 or tricyclohexylborane 4 in THF solution at room temperature in the presence of oxygen in the air as radical initiator generate high yields of trans-alkenes (E)-3 or (E)-5. Medium to high yields of different (E)-alkenes (E)-5, 7, 10, 12, and 14 also can be prepared when 1 reacts with different radicals, prepared from secondary alkyl iodides 6 and 8 or tertiary alkyl iodides 9, 11, and 13, in the presence of 2 and air as radical initiator. The generation of the only product (E)-alkenes can be explained by the generation of the benzylic radical A and/or B as the intermediate only and the mechanism is similar to Scheme 1. Both (E)- and (Z)-16a-c are generated when (E)- and (Z)-15a-c are used to react with adamantyl radical under similar conditions. Only (Z)-16d was observed when either (E)- or (Z)-15d was used to react with adamantyl radical. The generation of the (E)- and/or (Z)-alkenes can be explained by the free rotation of the A and/or B to generate A' and/or B' and vice versa, and the mechanism is proposed to be a free-radical reaction via NO2/alkyl substitution and is shown as Scheme 2.
authors.affiliation: Department of Chemistry, National Taiwan Normal University, 88, Sec. 4, Tingchow Road, Taipei, Taiwan 116, Republic of China.
authors.forename: J T
authors.initials: JT
authors.lastname: Liu
authors.forename: Y J
authors.initials: YJ
authors.lastname: Jang
authors.forename: Y K
authors.initials: YK
authors.lastname: Shih
authors.forename: S R
authors.initials: SR
authors.lastname: Hu
authors.forename: C M
authors.initials: CM
authors.lastname: Chu
authors.forename: C F
authors.initials: CF
authors.lastname: Yao