Asymmetric Aza-Claisen Rearrangement between Enantioenriched α-Chiral Allylamines and Allenones.

An unprecedented asymmetric aza-Claisen rearrangement between enantioenriched α-chiral allylamines and allenones was found to proceed in the absence of catalysts and additives at room temperature. The rearrangement, followed by hydrolysis, provides convenient access to structurally diverse δ-chiral ß-diketones in good to excellent yields with excellent retention of enantiopurity. This protocol proved powerful for the construction of an all-carbon quaternary stereocenter with high enantiopurity.

Catalytic allylation of stabilized phosphonium ylides with primary allylic amines.

A range of ketone-stabilized phosphonium ylides were allylated with high regioselectivity by primary allylic amines in the presence of 5 mol % Pd(PPh3)4 and 10 mol % B(OH)3, and subsequent one-pot Wittig olefination gave structurally diverse α,ß-unsaturated ketones in good to excellent overall yields with excellent E selectivity. The one-pot allylation/olefination reaction was extended to ester- and nitrile-stabilized phosphonium ylides by replacing B(OH)3 with TsOH, and the corresponding α,ß-unsaturated esters and nitriles were obtained in moderate overall yields.

Strain-release C-C bond cleavage enables the [2,3]-sigmatropic rearrangement of tertiary allylamines.

A new strategy has been established for the [2,3]-sigmatropic rearrangement of quaternary allylammonium ylides, generated in situ from tertiary allylamines and a bicyclo[1.1.0]butane via strain-release C-C bond cleavage. A range of tertiary allylamines with an acidic α-C-H bond participated in the 1-sulfonylbicyclo[1.1.0]butane-mediated [2,3]-sigmatropic rearrangement, delivering structurally diverse N-cyclobutyl homoallylamines in moderate to excellent yields.

Nucleophilic addition of tertiary propargylic amines to arynes followed by a [2,3]-sigmatropic rearrangement.

In the presence of 2-(trimethylsilyl)aryl triflates as aryne precursors under mild conditions, a range of tertiary propargylic amines bearing electron-withdrawing groups were converted to quaternary propargylic ammonium ylides followed by a [2,3]-sigmatropic rearrangement to afford structurally diverse amino-substituted allenes or conjugated dienes, depending on their structure, in moderate to good yields.

TfNHNHBoc as a SCF3 source for the sulfenylation of indoles.

An unprecedented use of trifluoromethanesulfonyl hydrazides as effective SCF3 sources has been established in the sulfenylation of indoles. A range of substituted indoles participated in CuCl-catalyzed oxidative sulfenylation reaction with TfNHNHBoc in the presence of dimethyl sulfoxide to furnish structurally diverse 3-indolyl trifluoromethyl thioethers in moderate to good yields with very high regioselectivity.