Synthesis of Arylglycine and Mandelic Acid Derivatives through Carboxylations of α-Amido and α-Acetoxy Stannanes with Carbon Dioxide

Abstract

Incorporation reactions of carbon dioxide (CO(2)) with N-Boc-α-amido and α-acetoxy stannanes were developed using CsF as a mild tin activator. Monoprotected α-amido stannanes could be used, and the corresponding arylglycine derivatives were obtained in moderate-to-high yields under 1 MPa (10 atm) of CO(2) pressure. α-Acetoxy stannanes also underwent carboxylation to afford mandelic acid derivatives in excellent yields under ambient CO(2) pressure. Both transformations enabled the synthesis of α-tertiary and α-quaternary carboxylic acid derivatives. In addition, the chirality of (S)-N-tert-butylsulfonyl-α-amido stannanes was transferred with up to 90% inversion of configuration at 100 °C.

Enantioselective Incorporation of CO2: Status and Potential

“…In 2012, the Sato group prepared asymmetric amino and mandelic acid derivatives from α-amido and α-acetoxy stannanes, respectively, using CsF as a tin-activator. 44 The chirality of (S)-N-tert-butylsulfonyl-α-amido stannanes was transferred (with retention of complex followed by carboxylation. 46 Interestingly, the asymmetric induction occurs at the postlithiation step, which was proven by deuterium-labelling on the benzylic position of benzyl methyl ether.…”

Syntheses of α‐Amino Acids by Using CO2 as a C1 Source

“…For the synthesis of α‐amino acids, monoprotected α‐amino acids, and in particular N ‐Boc derivatives, are much more useful than bis‐protected α‐amino acids, because conventional peptide synthesis employs N ‐Boc‐ or N ‐Fmoc‐amino acids (Fmoc=9‐fluorenylmethyloxycarbonyl), owing to the ease of protection and deprotection sequences (e.g., Merrifield peptide synthesis). To prepare this useful type of α‐amino acid, N ‐Boc‐α‐amino stannanes are thought to be reasonable intermediates . Nevertheless, when n BuLi is employed for monoprotected N ‐Boc‐α‐amino stannane in Sn/Li‐exchange reactions, deprotonation of the acidic amide N−H bond initially occurs to generate an amido anion.…”

Efficient Synthesis of Mandel Acetates by Electrochemical Carboxylation of Benzal Diacetates

“…Carbon dioxide, on the other hand, would also be a useful and favorable carbon source for synthesis of mandelic acid since it is a non‐toxic, abundant, economical, and environmentally benign C1 chemical reagent . There are a few examples of synthesis of mandelic acid and its derivatives using carbon dioxide as a carbon source of the carboxyl group by conventional chemical methods . Because of chemical stability of carbon dioxide, complicated or highly‐reactive reagents under severe or harsh reaction conditions would be frequently necessary.…”