Study On The Highly Efficient Conversion Of ?-Diazoacetates

As one kind of the most important intermediates in organic syntheses,diazo compounds have been considered to be multifunctional reagents.However,compared with other diazo compounds,?-alkyl substituted?-diazoacetates have much more reactive sites.This paper mainly focuses on the two highly catalytic reactions of?-diazoacetates.?1?Metal-free Lewis Acid TrBF₄-catalyzed 1,2-hydride migration of?-diazoacetates has been developed,affording?Z?-?-?-unsaturated esters in good yields and with high regioselectivities.And the reaction of the gram scale also worked well in87%yield and excellent Z-selectivity with up to Z:E=96:4.On the basis of mechanism experiments,it was found that the harnessing of ion-pair for stereoselectivity control.In addition,TrBF₄ efficiently catalyzed Roskamp reaction of?-diazoacetates with aldehydes,giving diverse?-branched-?-ketocarbonyls.?2?Visible-light promoted[2+1]and[2+2]cycloaddition reactions of?-diazoacetates with olefins have been also developed.Under blue LEDs irradiation,Ir?ppy?₃ could catalyzed[2+1]cyclopropanation of?-diazoacetates and olefins,affording functionalized various cyclopropanes with up to 97%yield.Moreover,It was found that Rh₂?OAc?₄ and Ir?ppy?₃ could synergistically catalyze the[2+2]cycloaddition of?-diazoacetates and olefins,obtaining excellent yield with up to 84%and high regioselectivity with up to 10:1 d.r..In addition,estrone-and vitamin E-derived cyclobutanes were also obtained in good yields.A number of experimental observations revealed that the[2+1]and[2+2]cycloaddition were achieved through energy transfer and single electron transfer,respectively.