Yonehara Fumi, Kido Yoshiyuki, Sugimoto Hiraku, Morita Satoshi, Yamaguchi Masahiko
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
J Org Chem. 2003 Aug 22;68(17):6752-9. doi: 10.1021/jo030093d.
GaCl(3) catalyzes the aromatic alkylation of naphthalene or phenanthrene using cycloalkanes. The C[bond]C formation predominantly takes place at the least hindered positions of the substrates, and equatorial isomers regarding the cycloalkane moiety are generally obtained. The reaction of bicyclo[4.4.0]decane and naphthalene occurs at the 2-position of naphthalene and at the 2- or 3-carbons of the cycloalkane, and the products possess a trans configuration at the junctures and an equatorial configuration at the naphthyl groups. Notably, cis-bicyclo[4.4.0]decane turns out to be much more reactive than the trans isomer, and a turnover number "TON" up to 20 based on GaCl(3) is attained. 1,2-Dimethylcyclohexane reacts similarly, and the cis isomer is more reactive than the trans isomer. Monoalkylcycloalkanes react at the secondary carbons provided that the alkyl group is smaller than tert-butyl. Adamantanes react at the tertiary 1-position. The alkylation reaction is considered to involve the C[bond]H activation of cycloalkanes with GaCl(3) at the tertiary center followed by the migration of carbocations and electrophilic aromatic substitution yielding thermodynamically stable products. The stereochemistry of the reaction reveals that GaCl(3) activates the equatorial tertiary C[bond]H rather than the axial tertiary C[bond]H.
氯化镓（GaCl₃）催化萘或菲与环烷烃的芳基烷基化反应。碳 - 碳键的形成主要发生在底物位阻最小的位置，并且通常得到环烷烃部分为平伏键异构体的产物。双环[4.4.0]癸烷与萘的反应发生在萘的2 - 位以及环烷烃的2 - 或3 - 位碳上，产物在连接点处具有反式构型，在萘基处具有平伏键构型。值得注意的是，顺式双环[4.4.0]癸烷的反应活性比反式异构体高得多，基于氯化镓（GaCl₃）的转化数（“TON”）可达20。1,2 - 二甲基环己烷的反应情况类似，顺式异构体比反式异构体更具反应活性。单烷基环烷烃在仲碳上发生反应，前提是烷基小于叔丁基。金刚烷在叔碳1 - 位发生反应。该烷基化反应被认为涉及环烷烃与氯化镓（GaCl₃）在叔碳中心发生碳 - 氢键活化，随后碳正离子迁移和亲电芳香取代反应，生成热力学稳定的产物。反应的立体化学表明，氯化镓（GaCl₃）活化的是平伏键叔碳 - 氢键而非直立键叔碳 - 氢键。
