Lewis base mediated halogenation/semipinacol rearrangement of diazo compounds: new access to α-halo-quaternary ketones.

A novel halogenation/semipinacol rearrangement of α-diazo alcohol catalyzed by Lewis base has been developed through a carbene-free mechanism. This semipinacol transposition, initiated by an electrophilic halogenation (X = Cl(+), Br(+), and I(+)) of diazo carbon event, furnished a convenient synthetic route for the efficient synthesis of α-halo-quaternary ketones under mild conditions.

Highly enantioselective synthesis of bisoxindoles with two vicinal quaternary stereocenters via Lewis base mediated addition of oxindoles to isatin-derived ketimines.

A highly efficient asymmetric organocatalytic addition of 3-substituted oxindole to isatin-derived ketimine is reported with excellent stereocontrol (>99 : 1 dr, >99% ee) under mild conditions. This method provides access to the bisoxindole structure moiety with two vicinal quaternary stereogenic centers.

Visible-light-induced direct C(sp3)-H difluromethylation of tetrahydroisoquinolines with the in situ generated difluoroenolates.

An effective approach to C1-difluoromethylated tetrahydroisoquinoline derivatives has been developed through C-H functionalization of tertiary amines by visible-light photoredox catalysis. This method uses stable, easily obtained α,α-difluorinated gem-diol as the CF2 source. The corresponding products were obtained in moderate to high yields at ambient temperature.

Organocatalytic one-pot synthesis of highly substituted pyridazines from Morita-Baylis-Hillman carbonates and diazo compounds.

A biologically inspired organocatalytic one-pot synthesis of highly functionalized pyridazines, which are ubiquitous structural units in a number of biologically active compounds, has been developed by starting from readily available diazo compounds and Morita-Baylis-Hillman (MBH) carbonates. Under mild reaction conditions, this synthetic route tolerated significant substrate variation to deliver a broad range of substituted products, including CF3 -substituted pyridazines derivatives. Moreover, the introduction of trifluoromethyl groups into the ring of pyridazine could be completed conveniently from 2,2,2-trifluorodiazoethane.