Selectivity control in alkylidene carbene-mediated C-H insertion and allene formation.

Regioselectivity of alkylidene carbene-mediated C-H insertion was explored utilizing electronic, conformational, steric, and stereoelectronic effects. Relying on these factors, highly regio- and chemoselective carbene insertion reaction of C-H bonds in different environments could be obtained. The observed selectivity clearly indicates that an electronic effect plays a more important role than steric effect. In general, C-H bonds in conformationally rigid cyclic environments are less reactive than those in acyclic systems toward carbene insertion, and in this situation, a competing intermolecular reaction between alkylidene carbene and trimethylsilyldiazomethane led to the formation of allenylsilanes. The formation of allenylsilane becomes more favorable as the concentration of reaction becomes higher, as well as the C-H bonds undergoing insertion becomes electronically and conformationally deactivated.

Highly diastereroselective synthesis of dihydrofurans and dihydropyrroles via pyridine catalyzed formal [4+1] annulation.

A pyridine-catalyzed ylide cyclization affording dihydrofurans and dihydropyrroles has been developed. In the presence of a catalytic amount of pyridine and Fe(Tcpp)Cl, α-ylidene-ß-diketones and α,ß-unsaturated imines react with diazoacetates providing dihydrofurans and dihydropyrroles respectively, in up to 96% yield with high diastereoselectivities.

Highly selective ylide-initiated Michael addition/cyclization reaction for synthesis of cyclohexadiene epoxide and vinylcyclopropane derivatives.

On the basis of the reactions of camphor-derived sulfur ylide with alpha,beta-unsaturated ketone, highly efficient and selective synthesis of optically active cyclohexadiene epoxides and vinylcyclopropanes with excellent diastereoselectivities, moderate to high enantioselectivities, and yields has been achieved.

One-pot highly diastereoselective synthesis of cis-vinylaziridines via the sulfur ylide-mediated aziridination and palladium(0)-catalyzed isomerization.

Highly diastereoselective synthesis of cis-trisubstituted vinylaziridines containing a quaternary carbon center is realized by a one-pot protocol in which the combination of sulfur ylide-mediated aziridination of cyclic ketimines and Pd(0)-catalyzed isomerization is employed successfully.

Stereoelectronic effect for the selectivity in C-H insertion of alkylidene carbenes and its application to the synthesis of platensimycin.

A systematic study of C-H insertion reactions with variously substituted and conformationally constrained substrates was carried out. High selectivity in the insertion between two competing C-H bonds caused by a strong stereoelectronic effect of an oxygen substituent was achieved. This regioselective C-H insertion reaction was employed as a platform to develop a concise asymmetric synthesis of platensimycin.

Highly diastereoselective and enantioselective formal [4 + 1] ylide annulation for the synthesis of optically active dihydrofurans.

On the basis of the reactions of camphor-derived sulfur ylide with alpha-ylidene-beta-diketones, highly efficient and selective synthesis of optically active dihydrofurans has been achieved.

Highly enantioselective synthesis of isoxazoline N-oxides.

The reaction of cinchonidine (cinchonine)-derived ammonium salts with nitroolefins in the presence of Cs2CO3 to afford optically active isoxazoline N-oxides with excellent ee and high de values has been developed.

Telluronium salts mediated aziridination of chiral N-tert-butylsulfinylimines: highly stereoselective synthesis of optically active vinylaziridines.

[reaction: see text] Optically active cis-2-substituted vinylaziridines are synthesized by the reaction of N-tert-butylsulfinylimines with telluronium ylides with excellent diastereoselectivity in good to excellent yields.

The Michael addition-elimination of ylides to alpha,beta-unsaturated imines. Highly stereoselective synthesis of vinylcyclopropanecarbaldehydes and vinylcyclopropylaziridines.

The Michael addition-elimination of ylide to alpha,beta-unsaturated imines leads to a highly diastereoselective and enantioselective synthesis of vinylcyclopropanecarbaldehydes in good to high yields for the first time. A sequential cyclopropanation-aziridination protocol for the preparation of cyclopropylaziridines is also developed with good diastereoselectivity in good to high yields.