T-BuOCl Promoted Chloroesterification Of Allenes

Allenes,is a unique compounds with two contiguous double bond structures.Compared with other unsaturated compounds such as alkene and alkyne,the reactivity of allenes is more active due to it’s special structure.By adjusting the electronic effect and stereoscopic effect of the substituents on the two terminal carbons of allenes,the rich and diverse reaction activities and selectivity can be realized,which is of significance in organic chemistry.In various studies on the chemical properties of allenes,hydrofunctionalization and difunctionalization of allenes have aroused wide interest.All kinds of functionalized allyl products can be directly and efficiently synthesized by this method with high selectivity.Allyl ester is an important compound,which widely exists in natural products.As an important intermediate in organic synthesis,allyl ester has been widely used in biological pharmaceutical and organic synthesis.This compounds can be synthesized through the chloroesterification reaction of the allenes,and a chlorine atom can be introduced into the molecule,which is conducive to the subsequent conversion.The reactions of（propa-1,2-dien-1-yloxy）benzene（1a）and benzoic acid（2a）with tert-butyl hypochlorite were selected as model reactions.The effect of solvents,molar ratio of reactant,the amount of tert-butyl hypochlorite and temperature were systematically investigated.The optimum reaction conditions are as follows:the addition of terminal phenoxyallene（1a,0.45 mmol,1.5 equiv.）with carboxylic acids（2a,0.3 mmol,1.0 equiv.）and t-Bu OCl（3 equiv.）was conducted in CCl₄ at RT for 3 h.Under the optimized reaction conditions,benzoic acids bearing electron-donating groups,electron-withdrawing groups,and large steric hindrance substituents,and alkane smoothly underwent the target three-component addition.Phenoxyallenes bearing electron-donating group,electron-withdrawing group,polysubstituted and fused rings also smoothly underwent the target three-component addition.The easy availability of raw materials,mild conditions,excellent compatibility of functional groups and metal-free make the reaction have a good application prospect.The target product was also obtained in 86%yield in gram scale reaction,.At the same time,the experimental study and theoretical calculation of the reaction mechanism showed that phenoxyallene,carboxylic acid and tert-butyl hypochlorite experienced a three component cooperative reaction process.