A practical access to acyl radicals from acyl hydrazides

Abstract

Various acyl radicals can be generated from the corresponding acyl triphenylmethyldiazo derivatives, produced by in situ oxidation of hydrazide precursors with phenylseleninic acid.

Reductive Chlorination and Bromination of Ketones via Trityl Hydrazones

“…Rather than introducing the chloride through nucleophilic displacement of an activated alcohol, with the attendant difficulties and complications noted above, the idea was to introduce the chlorine first and then, through the generation of a reactive intermediate, add a hydrogen atom. This concept was expected to be realized through the use of hydrazone chemistry (Figure a) . The reaction of a trityl hydrazone with a chloronium source was expected to give a chlorodiazene ( 5 ), which upon thermolysis would extrude N 2 to generate a trityl radical and the sought after reactive intermediate, the α‐chlorocarbinyl radical 6 .…”

A New Synthesis of Thioflavanones from Thiosalicylic Acid

“…mp 56-57 °C (lit. 4,142.1,138.4,133.7,130.4,129.2,129.0,128.5,127.4,127.2,125.2,46.7,45.5; 157.9,141.8,140.6,134.2,130.4,130.2,128.8,127.6,125.6,118.3,115.5,114.7,46.1,44.3; 148.5, 140.8, 140.6, 134.0, 133.5, 130.3, 130.1, 129.3, 127.3, 125.7, 123.5, 122.6, 46.1, 44.6;FT-IR (KBr) 3066, 1678(C=O), 1585, 1528, 1436, 1350, 1084, 728 cm 7.33-7.47 (m, 3H), 7.16-7.30 (m, 2H), 7.01-7.11 (m, 2H) 160.9, 141.8, 134.2, 133.7, 130.3, 129.2, 127.2, 125.3, 116.1, 115.8, 46.7, 44.7;FT-IR (KBr) 3060, 2893, 1676(C=O), 1592, 1508, 1435, 1286, 1228, 1084 6, 142.2, 138.3, 135.4, 133.6, 130.4, 129.6, 129.2, 127.3, 127.2, 125.1, 46.8, 45 6,159.6,142.3,133.6,130.4,130.1,129.2,128.6,127.2,125.2,…”

“…5 The construction of thiochroman-4-one rings is also performed by the acyl radical cyclization of 2-allylthiotriphenylhydrazides 6 at high temperature in multiple steps from thiosalicylic acid. Alternatively, thioflavanones are synthesized by the catalytic hydrogenation 7 of thioflavones, derived from the condensation of thiophenols and β-keto esters 8 or the intramolecular Wittig cyclization of salicilate thioesters, 9 with H 2 /Pd-C, but the desired products are obtained in low yields with side products.…”

Acyl Radical Chemistry via Visible-Light Photoredox Catalysis

“…4 , Conventional approaches to the generation of acyl radicals, however, generally require harsh reaction conditions such as UV irradiation or high temperatures. 5 One way to access these intermediates is by generation of alkyl radicals from alkyl iodides through photochemical or thermal initiation and subsequent carbonylation by CO (Scheme 1, method A). The use of acyl selenides in the presence of an organotin reagent such as Bu 3 SnH together with a radical initiator 4a, 6 is an alternative means of generating acyl radicals (method B).…”