Cheng Ming Chu

A convenient new procedure for converting primary amides into nitriles

An operationally simple and high-yielding procedure has been developed for the conversion of primary amides to the corresponding nitriles, using ethyl dichlorophosphate/DBU as the mild dehydrating agent.

Generation of nitroalkanes, hydroximoyl halides and nitrile oxides from the reactions of β-nitrostyrenes with Grignard or organolithium reagents

Abstract The β-nitrostyrenes 1 or 2 react with Grignard or organolithium reagents in ether or THF solution to generate by 1,4-addition the intermediate nitronates A . When A is treated with dilute hydrochloric acid, high yields of the nitroalkanes 3 (and oximes 4 ) or 5 are obtained. Hydroximoyl halides 6, 8 or nitrile oxides 7 can be isolated when the intermediate A is slowly added to the ice cold concentrated hydrohalic acid. The same products 6 and/or 7 are observed if the nitronates, generated from the substrate 1a , are added to 85% aqueous H 2 SO 4 but only the hydrolyzed carboxylic acids 9 are generated when the β-nitrostyrenes 2 are reacted with Grignard reagents and worked up under the same condition. The nitrile oxides 7 can undergo 1,3-dipolar cycloaddition with alkenes or alkynes to generate 2-isoxazolines or isoxazoles. A one-pot synthesis of the [n,3,0] bicyclic (n = 3 or 4) compounds 23–27 by intramolecular nitrile oxide-olefin cycloadditions is reported.

Free radical reactions to generate alkenes and/or ionic reactions to generate hydroximoyl chlorides when β-nitrostyrenes react with triethylaluminium or diethylaluminium chloride

β-Nitrostyrenes 1 react with triethylaluminium or diethylaluminium chloride in diethyl ether solution and under nitrogen or argon to generate the alkenes 2 and the hydroximoyl chlorides 3 after work-up with ice-cold, conc. hydrochloric acid. The formation of the alkenes 2 is proposed to be a free-radical reaction via NO2/alkyl substitution since the yields of the alkenes 2 are increased in the presence of benzoyl peroxide (Bz2O2) and decreased in the presence of galvinoxyl. Only the alkenes 2 are produced with a high stereoselectivity for the E isomers when β-nitrostyrenes react with triethylaluminium in the presence of one to two equivalents of Bz2O2 as free-radical initiator. The mechanism of the generation of the hydroximoyl chlorides 3 is proposed to proceed through a 1,4-addition pathway to produce nitronates A, then the protonated nitronates B or the nitroso cations C are trapped by chloride ion to form the final products. The yields of compounds 3 are also improved by the presence of Lewis acids such as MgCl2. Medium to high yields of the hydroximoyl chlorides 3 and traces or low yields of the alkenes 2 are generated when triethylaluminium or diethylaluminium chloride react with β-nitrostyrenes in the presence of three equivalents of MgCl2 under argon.