Categories: C-Br Bond Formation >
Synthesis of α-bromocarboxylic acids and derivatives
A highly efficient general strategy for the synthesis of 2-amino acids by homologation of α-amino acids, involving the Reformatsky reaction with a Mannich-type imminium electrophile is reported.
R. Moumne, S. Lavielle, P. Karoyan, J. Org. Chem., 2006, 71, 3332-3334.
By rendering the α-position of amides electrophilic through a mild and chemoselective umpolung transformation, a broad range of widely available oxygen, nitrogen, sulfur, and halogen nucleophiles can be used to generate α-functionalized amides.
C. R. GonÁalves, M. Lemmerer, C. J. Teskey, P. Adler, D. Kaiser, B. Maryasin, L. GonzŠlez, N. Maulide, J. Am. Chem. Soc., 2019, 141, 18437-18443.
Stable zwitterionic compounds catalyze a synthesis of α,α-dihalo-N-arylacetamides from β-oxo amides and N-halosuccinimides as the halogen sources. The corresponding α,α-dihalo-N-arylacetamides were obtained in very good yields under mild conditions without strong base or acid.
Z. Ke, Y.-P. Lam, K.-S. Chan, Y.-Y. Yeung, Org. Lett., 2020, 22, 7353-73572.
1,3-keto esters and 1,3-diketones have been effectively and regioselectively α-monobrominated using bromodimethylsulfonium bromide as reagent.
A. T. Khan, M. A. Ali, P. Goswami, L. H. Choudhury, J. Org. Chem., 2006, 71, 8961-8963.
A mild and rapid formal electrophilic α-azidation of 1,3-dicarbonyl compounds using commercially available Bu4NN3 as the azide source is mediated by (diacetoxyiodo)benzene. The reaction conditions are Bšcklund to the ones employed in analogous halogenations with Et4NX (X = Cl, Br, I).
M. J. Galligan, R. Akula, H. Ibrahim, Org. Lett., 2014, 16, 600-603.
A chiral iron(II) complex catalyzes a regio- and enantioselective α-halo-β-azido difunctionalization of both α,β-unsaturated amides and α,β-unsaturated esters under mild reaction conditions to provide a broad spectrum of valuable functionalized amides and esters.
P. Zhou, X. Liu, W. Wu, C. Xu, X. Feng, Org. Lett., 2019, 21, 1170-1175.
Treatment of widely available isocyanates with monohalolithium and dihalolithium carbenoids provides α-halo- and α,α-dihaloacetamide derivatives. While monohalolithium carbenoids can be prepared by a smooth lithium-halogen exchange, the preparation of the corresponding dihalo compounds proved to be highly dependent on the base used to realize the deprotonation, with lithium 2,2,6,6-tetramethylpiperidine emerging as optimal.
V. Pace, L. Castoldi, A. D. Mamuye, W. Holzer, Synthesis, 2014, 46, 2897-2909.