TEMPO-Catalyzed Direct Conversion of Primary Alcohols to α-Chloroacetals with TCCA Both as an Oxidant and a Chlorination Reagent

Abstract

Multistep reactions are often required for the transformation of alcohols to α-chloroacetals via the unstable intermediates aldehydes or α-halo aldehydes. Herein, we report a simplified procedure for practical synthesis of α-chloroacetals using 2,2,6,6-tetramethylpiperidine-1-oxyl as a catalyst and trichloroisocyanuric acid both as an oxidant and a chlorination reagent. The reaction is one-pot, solvent-free and high-yielding. In addition, the α-chloroacetals have been transformed to enol ethers through the elimination reaction in the presence of sodium.

Microwave-Assisted One-Pot Telescoped Synthesis of 2-Amino-1,3-thiazoles, Selenazoles, Imidazo[1,2-a]pyridines, and Other Heterocycles from Alcohols

“…A proposed mechanism, based on previous work by Giacomelli and co-workers for the oxidation step and Li and co-workers for the chlorination step, is shown in Scheme . First, the TEMPO radical is oxidized by TCCA to form the cationic intermediate I.…”

“…A proposed mechanism, based on previous work by Giacomelli and co-workers for the oxidation step 19 and Li and co-workers for the chlorination step, 28…”

“…1 H NMR (400 MHz, CDCl 3 ) δ 7.36− 7.30 (m, 5H), 7.30−7.23 (m, 3H), 7.20 (d, J = 7.1 Hz, 2H), 7.17− 7.12 (m, 1H), 5.84 (br s, 1H), 4.45 (s, 2H). 13 (S)-5-Phenyl-N-(1-phenylethyl)thiazol-2-amine (28). It was obtained as a white crystal (224.1 mg, 80%), mp 122.5−124.2 °C.…”

Formation of Enol Ethers by Radical Decarboxylation of α-Alkoxy β-Phenylthio Acids

“…A number of elimination processes are known in which a saturated ether bearing suitable groups at either or both the α and β positions are converted into enol ethers by base treatment or by reduction . Selenoxide fragmentation has also been used to convert a saturated ether into an enol ether. , …”