A facile and effective system has been developed for the regio- and chemoselective ring-opening/electrophilic functionalization of cyclopropanes through C-C bond activation by [bis(trifluoroacetoxy)iodo]benzene with the aid of the Lewis basic promoter p-toluenesulfonamide. The p-toluenesulfonamide-promoted system works well for a wide range of cyclopropanes, resulting in the formation of 1,3-diol products in good yields and regioselectivity.
Oxygen- and nitrogen-containing heterocyclic compounds are widely recognized as key components in many natural products and biologically relevant molecules, but often the problem comes down to methodologies in synthesizing them. Halocyclization of olefinic substrates is a promising strategy in the construction of O- and N-heterocyclic compounds, which further signifies the development of their asymmetric variants. Over the past years, our group has been devoted to this particular area of asymmetric electrophilic halocyclization with chalcogen-containing molecules as catalysts. In this account, the main focus is on the development of our novel chiral catalysts and applications derived from the reaction products.
An efficient and regioselective electrophilic bromolactonization of cyclopropylmethyl diesters using triphenylphosphine sulfide (Ph 3 PS) or diphenyl selenide (Ph 2 Se) as the Lewis basic chalcogenide catalyst has been developed. It was observed that Ph 3 PS favored the formation of antidiastereomer and yielded the multi-functional glactones. Interestingly, the diastereoselectivity was reversed when using Ph 2 Se as a catalyst where the syn-product instead of the anti-product was favored.
Abstract1,3‐difunctionalization of cyclopropane is an useful organic transformation. The corresponding 1,3‐difunctionalized products are synthetic synthons and building blocks in many organic syntheses. Many existing ring‐opening difunctionalization methodologies rely primarily on the use of donor−acceptor cyclopropanes, while the difunctionalization of unactivated cyclopropanes is less exploited. In this research, 1,3‐bromoesterification and 1,3‐bromoetherification of unactivated cyclopropanes were successfully achieved using N‐bromosuccinimide as the brominating agent with high yields and regioselectivity.magnified image
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