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Abstract We demonstrate that 2‐alkenylarylaldimines and ketimines undergo thermal 6π‐azaelectrocyclization to generate a wide range of azabicyclico‐quinodimethanes (o‐QDMs). Theseo‐QDMs exist as a hybrid of a diene and a benzylic diradical. The diradical nature was confirmed by their ability to undergo dimerization and react with H‐atom donor, 2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) and O₂. In addition, the interception of the diradicaloido‐QDMs by H‐atom transfer was used to synthesize five tetrahydroisoquinoline alkaloids and related bioactive molecules. The diene form can undergo [4+2] cycloaddition reactions with different dienophiles to generate bridged azabicycles in high endo:exo selectivity. The azabicyclico‐QDMs can be generated for [4+2] cycloaddition from a wide range of electronically and sterically varied 2‐alkenylarylimines, including mono, di, tri and tetrasubstituted alkenes, and imines derived from arylamine, alkylamine (1°, 2°, 3°), benzylamine, benzylsulfonamide andBoc‐amine. 

Abstract We disclose a Ni‐catalyzed cyclization/alkylmetal interception reaction in which products are readily linearized to permit regiodefined alkene dicarbofunctionalization. This method offers a convenient route to access 1,2‐oxasilolane heterocycles, 3‐hydroxysilanes and 4‐arylalkanols with the formation of C(sp³)−C(sp³) bonds at primary and secondary alkyl carbon centers. In this reaction, a silicon‐oxygen (Si−O) bond functions as a detachable linker that can be delinked with several hydride, alkyl, aryl and vinyl nucleophiles to create profusely functionalized 3‐hydroxysilanes. A silicon motif in the cyclic C(sp³)−Si−O construct in 1,2‐oxasilolane heterocycles can also be selectively deleted by Pd‐catalyzed hydrodesilylation affording Si‐ablated linear alcohol products reminiscent of vicinal ethylene dicarbofunctionalization with C(sp³) and C(sp²) carbon sources. 

A visible light-mediated, I2-catalyzed intermolecular transformation of alkenes, conjugated dienes, styrenes and alkynes to isooxazoline and isoxazole motifs with a-nitrocarbonyls and analogs is reported. The reaction is also applicable to 1,1-disubstituted terminal, 1,2-disubstituted internal and trisubstituted alkenes, and tolerates a range of functional groups including epoxides, heterocycles, phosphates, free alcohols and thiocyanates. Mechanistic studies reveal that a-nitrocarbonyls are first converted to -carbonyl radicals followed by their conversion to acyl nitrile oxides, which subsequently undergo [3 + 2] dipolar cycloaddition reactions with the unsaturated molecules.