A new synthetic approach to novel axially chiral benzocarbazole derivatives based on the highly enantioselective intramolecular hydroarylation (94-96% ee) of linked alkyne-indole systems by using the prevalent chiral base catalyst, cinchonidine or cinchonine, under unprecedented transition-metal-free conditions is described. The process is considered to involve chiral base catalysis for enantioselective transformation of the alkyne part to a reaction intermediate with an axially chiral vinylidene o-quinone methide (VQM) functionality, which subsequently effects stereospecific cyclization with the tethered indole moiety.

Herein, we describe a decarboxylative approach to the preparation of alkynylsilanes. Treatment of a silyl alkynoate in N,N-dimethylformamide (DMF) at 80 °C in the presence of catalytic amounts of CuCl and PCy3 produced the corresponding alkynylsilane in excellent yield. The copper-catalyzed decarboxylation proceeded smoothly with low catalyst loadings (0.5 mol % of CuCl and 1.0 mol % of PCy3) under mild reaction conditions and is easily scalable to gram quantities.

A new hetero [7]helicene 1 NN structured by a diazabenzodiheterole (pyrroloindole) ring core was successfully synthesized by catalytic domino cyclodehydrogenation with Pd(OAc) 2 and O 2 as the key step. Significantly, 1 NN was stereochemically stable at room temperature and could be subjected to optical resolution by chiral HPLC. Furthermore, kinetic analysis of 1 NN and DFT calculations on its variants revealed that the stereochemical stability of the benzodiheterole-based helicenes was highly dependent on not only the heteroaromatic ring component but also on the N-substituent of the pyrrole ring unit.

This communication describes the development of a metal-free catalytic decarboxylation of silyl alkynoates to alkynylsilanes. Treatment of a silyl alkynoate with a catalytic amount of tetrabutylammonium difluorotriphenylsilicate (TBAT) in N , N -dimethylformamide at 150 °C resulted in decarboxylation to give the corresponding alkynylsilane in good to excellent yield (75 → 95%). The TBAT system was applicable to the decarboxylation of sterically demanding silyl alkynoates such as tert -butyldiphenylsilyl 3-phenylpropiolate. Mechanistic studies revealed that the tetrabutylammonium alkynoate derived from TBAT and the silyl alkynoate act as a catalyst for the decarboxylation.

Structurally well-defined macrocyclic polysiloxanes with unique spirosiloxane units and regularly arranged Si–H groups were synthesized by B(C6F5)3-catalyzed dehydrocarbonative cross-couplings.