乙腈中的氯化钴(II)在温和的条件下催化多种醚与酰基卤的裂解,从而以高收率得到相应的酯。无环脂族醚裂解成相应的酯和氯化物,而环脂族醚产生ω-氯代酯。苄基醚可与苄基氯和苄基乙酰胺一起形成相应的酯。烯丙基和苄基醚裂解的比较研究表明,苄基醚可以在烯丙基醚存在下选择性裂解。可以以高度区域选择性的方式将环氧乙烷酮裂解为相应的β-氯代酯。乙烯基醚经历sp 2在这些条件下的-杂化的碳-氧键裂解。基于产物分析,讨论了涉及电子转移,随后进行O-酰化以及氯离子对S N 1或S N 2的攻击的机理。
Cobalt(II) chloride catalyzed acylation of alcohols with acetic anhydride: scope and mechanism
作者:Javed Iqbal、Rajiv Ranjan Srivastava
DOI:10.1021/jo00033a020
日期:1992.3
Cobalt(II) chloride catalyzes the acetylation of a variety of alcohols with acetic anhydride in excellent yield. Primary hydroxyl groups can be selectively acylated in the presence of secondary and tertiary ones while the secondary hydroxyl groups can be preferentially acetylated in the presence of tertiary ones. Tertiary alcohols have been found to give ketones, acetoacetates, olefins, and diketene in addition to the acetate. The beta-hydroxy esters and ketones can be acylated under these conditions without any elimination, and this reaction has been compared with 4-(dimethylamino)pyridine (DMAP)-mediated acylations where elimination of the resulting beta-acetoxy carbonyl compound is observed. A detailed investigation of the acylation of tertiary alcohols has revealed that these reactions proceed via a tertiary alkoxy radical and ketene. A mechanism for these acylations is proposed by invoking an electron-transfer process.