?-complexes of transition metals in organic synthesis. 1. cross-coupling of organotitanium compounds with allyl halides in the presence of palladium complexes
Palladium-catalyzed cross-coupling of benzyltitanium(IV) reagents with aryl fluorides
作者:Yan Li
DOI:10.1007/s00706-021-02881-w
日期:2022.2
The first palladium-catalyzed cross-coupling between benzyltitanium(IV) reagents with aryl fluorides is reported. A variety of diarylmethanes can be prepared in good to excellent yields by the catalyst system of PdCl2(dppf)2 associated with 1-[2-(di-tert-butylphosphanyl)phenyl]-4-methoxypiperidine. This reaction offered a highly efficient approach to diarylmethanes that are commonly found in life-changing
Getting up to speed: Both LiCl and the YCl3/MeLi catalyst system have an acceleration effect upon the substitution of silanesusingGrignardreagents (see scheme). The method provides access to benzyl‐, allyl‐, and arylsilanes in good yields from the starting silanes.
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。
Lewis acid-mediated nucleophilic alkylations on chiral [6,3a,4]oxadiazaindano[5,4-a]isoquinolines. Asymmetric synthesis of 1-alkyl substituted tetrahydroisoquinolines
Lewis acid-mediated nucleophilic alkylation of the chiral [6,3a,4]oxadiaza-indano[5,4-α]isoquinoline derivatives with various organometallic reagents leads to highly enantioselective synthesis of 1-alkyl substituted tetrahydroisoquinolines. This methodology was applied to the asymmetric synthesis of (−)-salsolidine and (+)-O-methylarmepavine.