2-Fluoroenones via an Umpolung Morita-Baylis-Hillman Reaction of Enones.

Several methods have been reported for the formation of 2-fluoroenones. However, all these methods involve laborious multiple-step sequences with resulting low overall yields. In this paper, we report the first formal enone-α-H to F substitution, leading to 2-fluoroenones in a single step from ubiquitous enones in 63-90% yield.

Controlling the regioselectivity of the ring opening of spiro-epoxyoxindoles for efficient synthesis of C(3)-N(1')-bisindoles and C(3)-N(1')-diindolylmethane.

An efficient strategy for the construction of both C(3)-N(1') bisindoles and C(3)-N(1') diindolylmethane has been explored via proper tuning of the nucleophilicity of indoline/indole to spiro-epoxyoxindole. Lewis acid-catalyzed highly regio- as well as chemoselective coupling at the C-3 centre of spiro-epoxyoxindoles with indolines furnishes C(3)-N(1') bisindoles whereas base mediated and Lewis acid-catalyzed regioselective coupling at the less hindered site of spiro-epoyoxindoles with indoles via the S2 mechanism provides C(3)-N(1') diindolylmethane.

Reagent-Controlled Reversal of Regioselectivity in Nucleophilic Fluorination of Spiro-epoxyoxindole: Synthesis of 3-Fluoro-3-hydroxymethyloxindole and 3-Aryl-3-fluoromethyloxindole.

A convenient and metal/catalyst-free approach for the reversal of regioselectivity in nucleophilic fluorination of a wide range of spiro-epoxyoxindoles has been reported simply by altering the nucleophilic fluoride reagents. Py·(HF) -mediated fluorination at the tertiary sp-C center of spiro-epoxyoxindole furnishes 3-fluoro-3-hydroxymethyloxindoles, whereas TBAF-mediated fluoride addition at the primary sp-C center renders 3-fluoromethyl-3-hydroxyoxindoles, which have been utilized for the synthesis of 3-aryl-3-fluoromethyloxindole.

Reversal of Selectivity in C3-Allylation and Formal [3 + 2]-Cycloaddition of Spiro-epoxyoxindole: Unified Synthesis of Spiro-furanooxindole, (±)-N-Methylcoerulescine, (±)-Physovenine, and 3a-Allylhexahydropyrrolo[2,3-b]indole.

An effective Lewis acid catalyzed regioselective C3-allylation and a formal [3 + 2]-annulation reaction of spiro-epoxyoxindoles have been developed and can be accessed simply by changing the reaction conditions. This method has been successfully employed for the synthesis of spiro(pyrrolidinyloxindole), 3a-allylhexahydropyrrolo[2,3-b]indole, and furanoindoline.

Efficient Synthesis of 3,3'-Mixed Bisindoles via Lewis Acid Catalyzed Reaction of Spiro-epoxyoxindoles and Indoles.

An efficient strategy for the synthesis of 3-(3-indolyl)-oxindole-3-methanol has been developed to achieve a Lewis acid catalyzed, highly regioselective ring opening of spiro-epoxyoxindoles with indoles. The method is used for the gram-scale formal total synthesis of (±)-gliocladin C.