Synthesis of carborane-fused cyclobutenes and cyclobutanes

Transmetalation of carborane-fused zirconacycles to Cu(Ⅱ) induces the C-C coupling reaction to form four-membered rings. This serves as a new efficient and general methodology for the generation of a series of carborane-fused cyclobutenes and cyclobutanes. A reaction mechanism involving transmetalation to Cu(Ⅱ) and reductive elimination is proposed.

CuBr-Promoted Tandem Cyclization/Trifluoromethylation of 2-Alkynylanilines: Efficient Synthesis of 3-Trifluoromethylindoles

A new efficient strategy for the synthesis of 3-trifluoromethyl-indoles was developed through tandem cyclization/trifluoromethylation of 2-alkynylanilines and Umemoto's reagent under effect of CuBr.The reaction features the use of cheap copper salt,mild reaction conditions and high yield of products.The preliminary mechanism study indicates the solvent dimethylacetamide acts as the role of dealkylation.

Palladium-Catalyzed Oxidative Annulation of 1-Hydroxy-o-Carborane withInternal Alkynes:Facile Synthesis of Carborane-Fused Oxaborolest

of main observation and conclusion A palladium catalyzed oxidative annulation of 1-hydroxy-o-carborane with internal alkynes via regioselective B(3)—H bond activation has been developed for facile synthesis of a series of QB-substituted carborane-fused oxaboroles.These molecules can undergo intramolecular oxidative dehydrogenative coupling to afford carborane-fused large n systems for potential applications in organic materials.The reaction mechanism is also proposed,involving hydroxy deprotonation,nucleopalladation of alkyne,regioselective electrophilic B—H substitution and reductive eiiimination.

Copper Catalyzed Asymmetric [4＋2] Annulations of D-A Cyclobutanes with Aldehydes

Copper catalyzed enantioselective [4＋2] annulations of D-A cyclobutanes and aldehydes have been developed. In the presence of a side arm modified chiral bisoxazoline （SaBOX） ligand, the [4＋2] annulations proceeded smoothly with a broad substrate scope. 22 examples were studied, leading to the corresponding products with various functional groups in 41%-99% yields with 〉99/1 dr and 90%-96% ee. The resulting product with two ester groups was mono-reduced, giving the corresponding product in excellent diastereoselectivity without loss of the enantiopurity.

Diastereo-and enantioselective palladium-catalyzed dearomative [4+2] cycloaddition of 3-nitroindoles

A Pd-catalyzed asymmetric decarboxylative[4+2]cycloaddition of 3-nitroindoles and vinyl benzoxazinanones is developed through a dearomatization approach.The reaction provides an efficient protocol for constructing a series of chiral tetrahydro-5H-indolo[2,3-b]quinolines in high yields and with excellent diastereo-and enantioselectivities.

Chiral iminophosphorane catalyzed asymmetric Henry reaction of α,β-alkynyl ketoesters

α,β-Alkynyl ketoesters were introduced to the enantioselective Henry reaction(nitroaldol condensation)with nitromethane catalyzed by tartaric acid derived chiral iminophosphoranes.As such,a variety of optically activeβ-nitro-substituted tertiary alcohols bearing alkyne moieties were obtained in good to excellent yields(42%–99%)and moderate to good level of enantiomeric excess(up to 87%ee).