Sadhan Jana

Bio: Sadhan Jana is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Trifluoromethylation & Catalysis. The author has an hindex of 10, co-authored 19 publications receiving 398 citations. Previous affiliations of Sadhan Jana include Indian Institute of Science & Indian Institutes of Science Education and Research.

Transition Metal Catalyzed Enantioselective C(sp2)–H Bond Functionalization

Abstract: Direct catalytic transformation of C–H bonds to new functionalities has provided a powerful strategy to synthesize complex molecular scaffolds in a straightforward way. Unstinting efforts of the sy...

Visible-light-induced oxidant and metal-free dehydrogenative cascade trifluoromethylation and oxidation of 1,6-enynes with water

Abstract: Generally, oxy-trifluoromethylation in olefins is achieved using oxidants and transition metal catalysts. However, labile olefins remain unexplored due to their incompatibility with harsh reaction conditions. Here, unprecedented light-induced oxidant and metal-free tandem radical cyclization–trifluoromethylation and dehydrogenative oxygenation of 1,6-enynes have been achieved using a photoredox catalyst, CF3SO2Na, and phenanthrene-9,10-dione (PQ), Langlois’ reagent (CF3SO2Na) and water as the oxygen source. This benign protocol allows for access to various CF3-containing C3-aryloyl/acylated benzofurans, benzothiophenes, and indoles. Moreover, the oxidized undesired products, which are inherently formed by the cleavage of the vinylic carbon and heteroatom bond, have been circumvented under oxidant free conditions. The mechanistic investigations by UV-visible and ESR spectroscopy, electrochemical studies, isotope labelling and density functional theory (DFT) suggest that light induced PQ produced a CF3 radical from CF3SO2Na. The generated CF3 radical adds to the alkene, followed by cyclization, to provide a vinylic radical that transfers an electron to PQ and generates a vinylic cation. Alternatively, electron transfer may occur from the CF3-added alkene moiety, forming a carbocation, which would undergo cationic cyclization to generate a vinylic carbocation. The subsequent addition of water to the vinylic cation, followed by the elimination of hydrogen gas, led to the formation of trifluoromethylated C3-aryloyl/acylated heterocycles.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts.

Abstract: Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.

Enantioselective Functionalization of Radical Intermediates in Redox Catalysis: Copper-Catalyzed Asymmetric Oxytrifluoromethylation of Alkenes

Abstract: A method for the efficient enantioselective oxytrifluoromethylation of alkenes has been developed using a copper catalyst system. Mechanistic studies are consistent with a metal-catalyzed redox radical addition mechanism, in which a C–O bond is formed via the copper-mediated enantioselective trapping of a prochiral alkyl radical intermediate derived from the initial trifluoromethyl radical addition.

Achieving Site-Selectivity for C-H Activation Processes Based on Distance and Geometry: A Carpenter's Approach.

Abstract: The ability to differentiate between highly similar C-H bonds in a given molecule remains a fundamental challenge in organic chemistry. In particular, the lack of sufficient steric and electronic differences between C-H bonds located distal to functional groups has prevented the development of site-selective catalysts with broad scope. An emerging approach to circumvent this obstacle is to utilize the distance between a target C-H bond and a coordinating functional group, along with the geometry of the cyclic transition state in directed C-H activation, as core molecular recognition parameters to differentiate between multiple C-H bonds. In this Perspective, we discuss the advent and recent advances of this concept. We cover a wide range of transition-metal-catalyzed, template-directed remote C-H activation reactions of alcohols, carboxylic acids, sulfonates, phosphonates, and amines. Additionally, we review eminent examples which take advantage of non-covalent interactions to achieve regiocontrol. Continued advancement of this distance- and geometry-based differentiation approach for regioselective remote C-H functionalization reactions may lead to the ultimate realization of molecular editing: the freedom to modify organic molecules at any site, in any order.

Arene diversification through distal C(sp2)-H functionalization.

Abstract: Transition metal-catalyzed aryl C-H activation is a powerful synthetic tool as it offers step and atom-economical routes to site-selective functionalization. Compared with proximal ortho-C-H activation, distal (meta- and/or para-) C-H activation remains more challenging due to the inaccessibility of these sites in the formation of energetically favorable organometallic pretransition states. Directing the catalyst toward the distal C-H bonds requires judicious template engineering and catalyst design, as well as prudent choice of ligands. This review aims to summarize the recent elegant discoveries exploiting directing group assistance, transient mediators or traceless directors, noncovalent interactions, and catalyst and/or ligand selection to control distal C-H activation.

Site-Selective C−H Arylation of Primary Aliphatic Amines Enabled by a Catalytic Transient Directing Group

Abstract: Transition-metal-catalysed direct C(sp3)−H functionalization of primary aliphatic amines is an attractive – but elusive – process that could provide efficient access to biologically and pharmaceutically important compounds. Now, a palladium-catalysed γ-arylation of primary alkylamines is achieved using an inexpensive, catalytic and transient directing group.