Three benzyltitaniumcompounds of (ArCH2)Ti(O-i-Pr)3 (Ar = Ph (1a), 4-MeOC6H4 (1b), 4-FC6H4 (1c)) were prepared and used as benzyl nucleophiles for coupling reactions with aromatic or heteroaromatic bromides. The simple catalytic system of 1 mol % Pd(OAc)2 and 2 mol % PCy3 worked efficiently for a wide variety of aromatic bromides, producing diarylmethanes in good to excellent yields of up to 96%.
三种benzyltitanium的(ARCH化合物2)的Ti(O-我-Pr)3(Ar为Ph(上1A),4- MeOC 6 H ^ 4(1B),4-FC 6 H ^ 4(1C制备))中并用作苄基亲核试剂,用于与芳族或杂芳族溴化物偶联反应。1 mol%Pd(OAc)2和2 mol%PCy 3的简单催化系统可以有效地用于各种芳族溴化物,以高达96%的优异收率生产二芳基甲烷。受阻芳族溴化物或含有吸电子取代基的芳族溴化物的偶联反应在3-6小时的较长反应时间内较慢。溴吡啶,溴呋喃或溴噻吩的杂芳族溴化物与1a或1b的苄基试剂反应需要更长的反应时间12–24 h或更高的反应温度80°C,从而产生吡啶基,呋喃基和噻吩基-芳基甲烷中等产量。
Selective Late‐Stage Hydrodefluorination of Trifluoromethylarenes: A Facile Access to Difluoromethylarenes
作者:Socrates B. Munoz、Chuanfa Ni、Zhe Zhang、Fang Wang、Nan Shao、Thomas Mathew、George A. Olah、G. K. Surya Prakash
DOI:10.1002/ejoc.201700396
日期:2017.4.26
A selective reductive monodefluorination reaction of trifluoromethyl arenes was developed. Mediated by magnesium metal, various difluoromethylated aromatics were accessed at room temperature in the presence of acetic acid. This protocol shows tolerance to a wide range of functional groups and it was applicable in late-stage hydrodefluorination of complex pharmaceutical compounds, affording the corresponding