Palladium‐Catalyzed Asymmetric Benzylic Alkylation of Active Methylene Compounds with α‐Naphthylbenzyl Carbonates and Pivalates

Abstract

AP d/(R)-H 8 -BINAP-catalyzed asymmetric benzylic alkylation of active methylene compounds has been developed. The reaction proceeds without the use of an external base,and the starting racemic diarylmethyl carbonates are converted into the optically active coupling products which contain the benzylic chiral stereocenter by ad ynamic kinetic asymmetric transformation (DYKAT). Additionally,w ith suitable carbonates bases,t he same palladium catalysis allows the corresponding pivalates to be adopted in the same DYKATprocess. Angewandte Chemie CommunicationsScheme 4. Palladium-catalyzed asymmetric benzylic alkylation of dimethyl malonate (2a)with secondary (heteroaryl)methyl pivalates (6). Scheme 3. Plausiblemechanism. L = (R)-H 8 -BINAP. The descriptor R L means the absoluteconfigurationo fthe ligand L. Angewandte Chemie Communications 6975 Angew.C hem. Int.E d. 2016, 55,6 973 -6977 2

Pd‐Catalyzed Umpolung of η3‐Benzylpalladium Enabled the Construction of All‐Carbon α‐Vinyl Quaternary Aldehydes

“…In contrast, other bidentate ligands L5 – L6 also proved to be reactive while giving rise to inferior results (Table 1, entries 3–4). The variation of palladium catalysts resulted in unsatisfactory results indicating the unique reactivity of [CpPd( η 3 ‐C 3 H 5 )] catalyst (Table 1, entry 5–8); similar promising reactivity of this palladium precursor was also observed by others in related benzylation reactions [8e,14] . A series of solvents were also investigated and no superior reaction outcomes were obtained as exemplified in entries 9–11 of Table 1.…”

Palladium-catalyzed enantioselective (2-naphthyl)methylation of azaarylmethyl amines

“…36 This is likely due to the greater difficulty forming the initial arene intermediate, (LG-CH 2 C 6 H 5 )-Pd(0), and the subsequent oxidative ionization of the leaving group with concomitant disruption of aromaticity. 37,38 Most of the nucleophiles employed in asymmetric benzylations are organozinc 39 and organoboron reagents. 40 Other strategies employ enolate derived nucleophiles 41,42 or decarboxylative benzylations.…”