A new approach to .alpha.,.alpha.-difluoro-functionalized esters
摘要:
The addition reaction of iododifluoroacetates to alkenes is initiated by copper powder (10-20 mol %) at 50-60-degrees-C. Both terminal and internal alkenes give good yields of adducts. The reaction is also applicable to alkenes containing a variety of functional groups, such as epoxy, hydroxy, ketone, ester, and phosphonate moieties. This reaction can be carried out either neat or in solvents such as hexane, benzene, acetonitrile, DMF, DMSO, and HMPA and is suppressed by p-dinitrobenzene and di-tert-butyl nitroxide. A single electron transfer initiated radical mechanism is proposed. In the presence of nickel dichloride hexahydrate, reduction of the adducts with zinc in moist THF provides the corresponding alpha,alpha-difluoro esters in good yields.
Nickel-catalyzed reaction of iododifluoroacetates with alkenes and zinc: a novel and practical route to .alpha.,.alpha.-difluoro-functionalized esters and .alpha.,.alpha.,.omega.,.omega.-tetrafluoro diesters
作者:Zhen Yu Yang、Donald J. Burton
DOI:10.1021/jo00045a027
日期:1992.9
lododifluoroacetates 1a-c react with alkenes and zinc in the presence of nickel dichloride hexahydrate in THF at room temperature or 60-degrees-C to give the corresponding alpha,alpha-difluoro esters in good yields. The reaction is also applicable to alkenes containing a variety of functional groups such as trimethylsilyl, hydroxy, ketone, and ester moieties. The reaction of 1 works well with dienes; the products formed depend on the length of chain of the dienes. 1,8-Nonadiene and 1,5-hexadiene afford the alpha,alpha,omega,omega-tetrafluoro diesters, while 1,6-heptadiene gave a mixture of ethyl 2,2-difluoro-8-nonenoate (19) and the cyclopentyl-substituted alpha,alpha-difluoro ester 20. When diallyl ether was used as a substrate, only the tetrahydrofuran derivative 21 was formed. The nickel-catalyzed reaction can be suppressed by p-dinitrobenzene and hydroquinone. A single electron transfer initiated radical mechanism is proposed.
YANG, ZHEN-YU;BURTON, DONALD J., J. FLUOR. CHEM., 45,(1989) N, C. 435-439
作者:YANG, ZHEN-YU、BURTON, DONALD J.
DOI:——
日期:——
A new approach to .alpha.,.alpha.-difluoro-functionalized esters
作者:Zhen Yu Yang、Donald J. Burton
DOI:10.1021/jo00017a026
日期:1991.8
The addition reaction of iododifluoroacetates to alkenes is initiated by copper powder (10-20 mol %) at 50-60-degrees-C. Both terminal and internal alkenes give good yields of adducts. The reaction is also applicable to alkenes containing a variety of functional groups, such as epoxy, hydroxy, ketone, ester, and phosphonate moieties. This reaction can be carried out either neat or in solvents such as hexane, benzene, acetonitrile, DMF, DMSO, and HMPA and is suppressed by p-dinitrobenzene and di-tert-butyl nitroxide. A single electron transfer initiated radical mechanism is proposed. In the presence of nickel dichloride hexahydrate, reduction of the adducts with zinc in moist THF provides the corresponding alpha,alpha-difluoro esters in good yields.
Copper catalyzed addition reaction of iododifluoroacetates to olefins
作者:Zhen-Yu Yang、Donald J. Burton
DOI:10.1016/s0022-1139(00)82877-8
日期:1989.12
The addition of iododifluoroacetates to alkenes is catalyzed by copper powder (10-20 mol %) at 50° to 60°C. The reaction can be carried out neat or in hexane or benzene as solvent. Both terminal and internal alkenes gave good yields (65-83%). Reduction of the adduct with tributyltin hydride provides the α, α-difluoroacetate.