Ni-Catalyzed Formal Cross-Electrophile Coupling of Alcohols with Aryl Halides
Direct coupling of unactivated alcohols remains a challenge in current synthetic chemistry. We herein demonstrate a strategy building upon in situ halogenation/reductive coupling of alcohols with aryl halides to forge Csp2-Csp3 bonds. The combination of 2-chloro-3-ethylbenzo[d]oxazol-3-ium salt (CEBO) and TBAB as the mild bromination reagents enables rapid transformation of a wide range of alcohols to their bromide counterparts within one to 5 min in CH3CN and DMF, which is compatible with the Ni-catalyzed cross-electrophile coupling conditions in the presence of a chemical reductant. The present method is suitable for arylation of a myriad of structurally complex alcohols with no need for prepreparation of alkyl halides. More importantly, the mild and kinetically rapid bromination process has shown good selectivity in the bromination/arylation of symmetric diols and less sterically hindered hydroxyl groups in polyols, thus offering promise for selective functionalization of diols and polyols without laborious protecting/deprotecting operations. The practicality of this work is also evident in the arylation of a number of carbohydrates, drug compounds, and naturally occurring alcohols.
Lin, Quan,Ma, Guobin,Gong, Hegui
p. 14102 - 14109
(2021/11/20)
Stereoselective radical Aryl migration reactions from sulfur to carbon
Stereoselective aryl migration reactions from sulfur in sulfonates and sulfonamides to C-centered radicals are reported. The 1,5-aryl migration from sulfur to differently substituted C-centered radicals could be performed with high yields and selectivities. Functionalized aryl groups could also be transferred by this new method. A model to explain the stereochemical outcome of the reaction is presented and some mechanistic aspects of this reaction are discussed. Aryl migration reactions from sulfur in sulfinates to carbon radicals were less efficient, and the corresponding migrations in aryl sulfoxides were not observed at all. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.