Synthesis Of Functionalized Cyclopropanes Based On A Dehydroxylative Radical Addition Strategy

Cyclopropanes occupy a vital position in organic synthesis and drug development due to their structural features(ring tension 27.5 kcal/mol)and reactivity.However,the construction of cyclopropane often requires diazo compounds and metal reagents.This thesis is devoted to the development of green and efficient strategies for the synthesis of functionalized cyclopropanes.The research is as follows:A method was developed to generate cyclopropanes from alcohols or 1-hydroxy sugars with allyl chloride derivatives under photo-mediated conditions.The alcohols form activated intermediates with NHC,which generate carbon radicals under blue light irradiation and photosensitizers.After radical addition to olefins,anions are formed by the radical polar cross-over process,and the anions close the ring to generate cyclopropanes.The advantages of the strategy are as the following: The reaction is applicable to various protected pyranoses and furanoses,and can be compatible with substrates such as primary,secondary,and tertiary alcohols,and has good tolerance to allyl chloride substituted with various functional groups(over 70 examples).The reaction operation is simple,and the conditions are mild,and does not require the use of expensive transition metals and hazardous reagents.It can be used for the late-stage modification of cholesterol,hydroxypropyl theophylline,L-menthol,and other natural products.Free radical trapping experiments and deuteration experiments using 1-hydroxy sugars as substrates showed that the reaction involves free radicals and anion intermediates.The work above enriches the synthesis method of C-glycosides and provides new ideas for synthesizing cyclopropane derivatives,which is beneficial for the chemical research related to cyclopropanes.