Cyanide-Free Cyanation of sp and sp-Carbon Atoms by an Oxazole-Based Masked CN Source Using Flow Microreactors.

This work reports a cyanide-free continuous-flow process for cyanation of sp and sp carbons to synthesize aryl, vinyl and acetylenic nitriles from (5-methyl-2-phenyloxazol-4-yl) boronic acid [OxBA] reagent as a sole source of carbon-bound masked -CN source. Non-toxic and stable OxBA reagent is generated by lithiation-borylation of bromo-oxazole, and the consecutive Suzuki-Miyaura cross-coupling with aryl, vinyl, or acetylenic halides and demasking [4+2]/retro-[4+2] sequence were successfully accomplished to give the desired cyano compounds with reasonably good yields in a four-step flow manner. A unique feature of this cyanation protocol in flow enables to cyanate a variety of sp and sp carbons to produce a broad spectrum of aryl acetonitrile.

Flow parallel synthesizer for multiplex synthesis of aryl diazonium libraries via efficient parameter screening.

The development of miniaturized flow platforms would enable efficient and selective synthesis of drug and lead molecules by rapidly exploring synthetic methodologies and screening for optimal conditions, progress in which could be transformative for the field. In spite of tremendous advances made in continuous flow technology, these reported flow platforms are not devised to conduct many different reactions simultaneously. Herein, we report a metal-based flow parallel synthesizer that enables multiplex synthesis of libraries of compounds and efficient screening of parameters.

Harnessing Nucleophilicity of Allenol Ester with p-Quinone Methides via Gold Catalysis: Application to the Synthesis of Diarylmethine-Substituted Enones.

A gold(I)-catalyzed protocol for intermolecular 1,6-conjugate addition of nucleophilic allenol ester generated in situ through [3,3]-sigmatropic rearrangement with p-quinone methides ( p-QMs) has been developed. The gold catalyst plays a dual role by the π-acid-triggered activation of alkynes and at the same time as a Lewis acid for activation of p-QMs toward nucleophilic attack. This method enables rapid access to a wide range of densely functionalized diarylmethine-substituted enones, a Morita-Baylis-Hillman (MBH) product with high selectivity, excellent yields, and broad substrate scope.

Unravelling the Nucleophilicity of Butenolides for 1,6-Conjugate Addition to p-Quinone Methides: A Direct Access to Diversely Substituted Butenolide-Derived Diarylmethanes.

A Lewis acid catalyzed regioselective C-C bond is constructed through β-addition of deconjugated butenolides with p-quinone methides in a 1,6-conjugate addition manner. Interestingly, Lewis acid catalyzed vinylogous Mukaiyama-Michael reaction of silyloxyfurans with p-QMs proceeds selectively through the α or γ position exclusively. The reaction is mild with broad substrate scope, thus allowing easy access to a wide range of bis-arylated α-/β-/γ-substituted butenolides.

Transition metal catalysis-a unique road map in the stereoselective synthesis of 1,3-polyols.

The present review summarizes recent diverse reactions employed in the formation of 1,3-polyols providing an overview of the mechanistic pathway and the enantioselectivity obtained, in terms of the properties of transition metals directly involved in the catalytic transformations and their interaction with various ligands.