Tanay Kesharwani

Bio: Tanay Kesharwani is an academic researcher from University of West Florida. The author has contributed to research in topics: Aryl & Aldehyde. The author has an hindex of 10, co-authored 24 publications receiving 618 citations. Previous affiliations of Tanay Kesharwani include Iowa State University & University College West.

A Copper‐Catalyzed Tandem Synthesis of Indolo‐ and Pyrrolo[2,1‐a]isoquinolines

Abstract: Transition-metal-catalyzed tandem reactions have emerged as a useful tool for the synthesis of multiring heterocyclic compounds because of the intriguing selectivity, atom economy, and exceptional ability to activate p systems, especially alkynes, towards intermolecular and intramolecular nucleophilic attack. Among the transition-metal-catalyzed reactions, palladium is extensively used because of its tolerance of many functional groups and its low toxicity. However, in recent years copper-catalyzed reactions have received considerable attention because of their efficiency and low costs. 5] The reported annulation chemistry for the synthesis of heterocycles from alkynes proceeds through p complexation of the alkyne and subsequent attack of the resulting h-metal complex onto the appropriate adjacent functionalized arene. 6] However, the synthesis of polyheterocycles by the nucleophilic addition of N heterocycles onto alkynes and subsequent in situ ring closure by C C bond formation is still unknown. Indolo[2,1-a]isoquinolines and pyrrolo[2,1-a]isoquinolines have unique nitrogen-containing tetracyclic and tricyclic structures, and their reduced and oxidized forms occur widely among natural products, biologically active pharmaceuticals, and p-conjugated functional materials, such as organic semiconductors and luminescent materials. The reported methods for the syntheses of indoloand pyrrolo[2,1-a]isoquinolines, typically require multistep syntheses and expensive reagents. Methods for the construction of these structures include well known benzyne reactions or the oxidative couplings of 1-benzylisoquinoline. F rstner and co-workers reported the synthesis of analogous isoquinolines by the cycloisomerization of biaryl alkynes using PtCl2, AuCl, AuCl3, GaCl3, or InCl3. [2a] Herein, we report the first coppercatalyzed synthesis of this class of heterocycles by the tandem addition of N heterocycles onto alkynes and subsequent intramolecular cyclization of the in situ generated enamine by C2 arylation. In continuation of recently developed methods for the copper-catalyzed N-arylation using benzotriazole as a ligand and the electrophilic cyclization of alkynes, 15] we hypothesized that the direct synthesis of polycyclic heteroaromatic compound 6 could occur in a one-pot reaction of N heterocycle 1 with ortho-haloarylalkyne 2 by sequential N C and C C bond formation under the proper conditions such that intermediate 5 would not have to be isolated (Scheme 1, route A). We also anticipated the possible formation of regioisomer 3 by initial arylation of N heterocycle 1 at the C2position by the ortho-haloarylalkyne 2 and subsequent intramolecular attack of the N heterocycle onto the carbon– carbon triple bond of the in situ generated intermediate 4 (Scheme 1, route B). This designed tandem reaction features the use of benzotriazole (L1) and benzotriazol-1-ylmethanol (L2) as novel and inexpensive ligands in copper-catalyzed reactions. To identify the optimal reaction conditions for the reaction, a number of copper catalysts, including CuI, CuCl, CuBr, Cu2O, and Cu(OAc)2, and several different organic solvents and ligands were examined in the reaction of 3methylindole (1a) with 2-bromophenyl-4-methoxyphenylethyne (2a ; Table 1). Interesting observations emerge from the data in Table 1. We first reacted 1 a (0.5 mmol) with 1.1 equivalents of 2a, 10 mol% of CuI, and 1.4 equivalents of KOtBu in 1.0 mL of DMF at 110 8C for 24 hours—the desired coupling product 3a was not observed (Table 1, entry 1). However, the addition of 20 mol% of ligand L1 to the reaction afforded the desired product 3a in a 65 % yield (Table 1, entry 2). The designed ligand L2, was subsequently found to be more effective than ligand L1 (Table 1, entry 3), and from entries 4 and 5 in Table 1 it is apparent that the solvent has a significant influence on the reaction. DMSO was found to be quite successful for the transformation as compound 3a was obtained in an 82 % yield when DMSO was used as the solvent instead of DMF (Table 1, entry 4). When we used toluene as the solvent, the desired product 3a was obtained in only a 38% yield (Table 1, entry 5). Different bases were tested in this reaction system, but KOtBu proved to be most effective (Table 1, entries 4, 6, and 7). The yield of [*] Dr. A. K. Verma, J. Singh, Dr. V. Tandon Dr. B. R. Ambedkar Center for Biomedical Research University of Delhi, Delhi 110007 (India) E-mail: averma@acbr.du.ac.in

Synthesis of 3,4-Disubstituted 2H-Benzopyrans Through C-C Bond Formation via Electrophilic Cyclization

Abstract: The electrophilic cyclization of substituted propargylic aryl ethers by I2, ICl, and PhSeBr produces 3,4-disubstituted 2H-benzopyrans in excellent yields. This methodology results in vinylic halides or selenides under mild reaction conditions and tolerates a variety of functional groups, including methoxy, alcohol, aldehyde, and nitro groups.

Synthesis of 2,3-Disubstituted Benzo[b]selenophenes via Electrophilic Cyclization

Abstract: 2,3-Disubstituted benzo[b]selenophenes have been prepared by the electrophilic cyclization of various 1-(1-alkynyl)-2-(methylseleno)arenes by Br2, NBS, I2, ICl, PhSeCl, PhSeBr, and Hg(OAc)2. This method tolerates a wide variety of functional groups, including alcohol, ester, nitrile, nitro, and silyl groups, and proceeds under exceptionally mild reaction conditions.

The Sonogashira Reaction: A Booming Methodology in Synthetic Organic Chemistry†

Abstract: 3.7. Palladium Nanoparticles as Catalysts 888 3.8. Other Transition-Metal Complexes 888 3.9. Transition-Metal-Free Reactions 889 4. Applications 889 4.1. Alkynylation of Arenes 889 4.2. Alkynylation of Heterocycles 891 4.3. Synthesis of Enynes and Enediynes 894 4.4. Synthesis of Ynones 896 4.5. Synthesis of Carbocyclic Systems 897 4.6. Synthesis of Heterocyclic Systems 898 4.7. Synthesis of Natural Products 903 4.8. Synthesis of Electronic and Electrooptical Molecules 906

Catalytic Functionalization of Indoles in a New Dimension

Abstract: 140 years ago Adolf von Baeyer proposed the structure of a heteroaromatic compound which revolutionized organic and medical chemistry: indole. After more than a century, indole itself and the complexity of naturally occurring indole derivatives continue to inspire and influence developments in synthetic chemistry. In particular, the ubiquitous presence of indole rings in pharmaceuticals, agrochemicals, and functional materials are testament to the ever increasing interest in the design of mild and efficient synthetic routes to functionalized indole derivatives. This Review emphasizes the achievements in the selective catalytic functionalization of indoles (C-C bond-forming processes) over the last four years.

Mitsunobu and Related Reactions: Advances and Applications

Abstract: 10. Patented Literature 2616 10.1. Esterification 2616 10.2. Ether Formation 2619 10.2.1. Etherification without Cyclization 2619 10.2.2. Etherification with Cyclization 2624 10.3. N-Alkylation 2625 10.4. Other Reactions 2627 11. Summary and Outlook 2628 12. Note Added in Proof 2628 13. Abbreviations Used in This Review 2629 14. Acknowledgments 2629 15. Supporting Information Available 2630 16. References 2630