ChemInform Abstract: Synthesis of Lepidoptera Pheromones

Abstract

Review: (217 refs.

Triphenylphosphine-2,4,4,6-tetrabromo-2,5-cyclohexadienone complex as a reagent for preparation of carboxylic acid bromides

“…On the basis of the results of previous studies [1][2][3][4][5], we presumed that the reaction of triphenylphosphine with 2,4,4,6-tetrabromo-2,5-cyclohexadienone (I) can be regarded as a halophilic process [1] leading to formation of a complex which reacts with carboxylic acid to give acyloxyphosphonium intermediate II and 2,4,6-tribromophenol (III). The subsequent decomposition of intermediate II affords the corresponding acyl bromide and triphenylphosphine oxide (Scheme 1).…”

“…The scope of application of such complexes for nucleophilic replacement of hydroxy group by halogen was demonstrated using various alcohols as examples [2,3]. Preparation of bromo derivatives is often necessary in fine organic synthesis.…”

“…We recently pro-posed a new bromophilic reagent, 2,4,4,6-tetrabromo-2,5-cyclohexadienone (I), which was known previously as a source of electrophilic and radical bromine species [4]. The complex formed by compound I and triphenylphosphine ensured regioand stereoselective nucleophilic substitution of hydroxy group in alcohols, and it turned out to be very promising for stereoselective replacement of hydroxy group in cage-like structures [2]. In the present communication we demonstrate the efficiency of the triphenylphosphine-2,4,4,6-tetrabromo-2,5-cyclohexadienone complex in nucleophilic substitution of the hydroxy group in carboxylic acids.…”

Regioselective Chlorination of Quinoline N‐Oxides and Isoquinoline N‐Oxides Using PPh3/Cl3CCN

“…More recently, PPh 3 and various halogenating agents, as combined reagents, have received significant attention for the preparation of N‐heterocyclic halides under acid‐free conditions. PPh 3 , in combination with chlorinating agents CCl 4 ,13a Cl 3 CCCl 3 ,13b Cl 3 CCOCCl 3 ,13c Cl 3 CCN13d and Cl 3 CCONH 2 13e,13f respectively has been utilized for the conversion of alcohols into chlorides. Likewise, PPh 3 /Br 3 CCO 2 Et and PPh 3 /Br 3 CCOBr 3 14 have been used to convert alcohols to alkyl bromides.…”