Short syntheses of 1-substituted dibenzothiophene derivatives.

The 1-substituted dibenzothiophene motif is an unusual substitution pattern that has previously been accessed via a multi-step synthesis. We demonstrate a simple one-pot preparation of 1-lithiodibenzothiophene from commercial materials via a cascade of two benzyne additions and conversion to several derivatives by addition of electrophiles. A chiral amine containing the 1-dibenzothiophene motif was also prepared.

Enantioselective Imine Reduction Catalyzed by Phosphenium Ions.

The first use of phosphenium cations in asymmetric catalysis is reported. A diazaphosphenium triflate, prepared in two or three steps on a multigram scale from commercially available materials, catalyzes the hydroboration or hydrosilylation of cyclic imines with enantiomeric ratios of up to 97:3. Catalyst loadings are as low as 0.