Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Ling-Ling Road, Shanghai, 200032, China.
Boston-Kenilworth LO Chemistry, Merck Research Laboratories , 33 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States.
J Am Chem Soc. 2015 Nov 18;137(45):14496-501. doi: 10.1021/jacs.5b09888. Epub 2015 Nov 5.
A new olefination protocol for transition-metal-free cross-coupling of two carbene fragments arising from two different sources, namely, a nonfluorinated carbene fragment resulting from a diazo compound and a difluorocarbene fragment derived from Ruppert-Prakash reagent (TMSCF3) or TMSCF2Br, has been developed. This gem-difluoroolefination proceeds through the direct nucleophilic addition of diazo compounds to difluorocarbene followed by elimination of N2. Compared to previously reported Cu-catalyzed gem-difluoroolefination of diazo compounds with TMSCF3, which possesses a narrow substrate scope due to a demanding requirement on the reactivity of diazo compounds and in-situ-generated CuCF3, this transition-metal-free protocol affords a general and efficient approach to various disubstituted 1,1-difluoroalkenes, including difluoroacrylates, diaryldifluoroolefins, as well as arylalkyldifluoroolefins. In view of the ready availability of diazo compounds and difluorocarbene reagents and versatile transformations of 1,1-difluoroalkenes, this new gem-difluoroolefination method is expected to find wide applications in organic synthesis.
已开发出一种新的烯烃化协议，用于无过渡金属的交叉偶联两种来自两个不同来源的卡宾片段，即由重氮化合物产生的无氟化卡宾片段和由 Ruppert-Prakash 试剂（TMSCF3）或 TMSCF2Br 衍生的二氟卡宾片段。这种偕二氟烯烃化通过重氮化合物对二氟卡宾的直接亲核加成进行，随后消除 N2。与以前报道的 TMSCF3 与重氮化合物的 Cu 催化偕二氟烯烃化相比，由于对重氮化合物和原位生成的 CuCF3 的反应性要求苛刻，该协议的底物范围较窄，这种无过渡金属的协议为各种取代的 1,1-二氟烯烃提供了一种通用且高效的方法，包括二氟丙烯酸酯、二芳基二氟烯烃以及芳基烷基二氟烯烃。鉴于重氮化合物和二氟卡宾试剂的易得性以及 1,1-二氟烯烃的多种转化，这种新的偕二氟烯烃化方法有望在有机合成中得到广泛应用。
