Department of Chemical Sciences
School of Natural Sciences

December 21, 2020 at 4.30 pm (Via Zoom)

Title :

Development of New Methods for Selective and Efficient Chemical Synthesis

Abstract :

In spite of the changing face of chemistry, the impact of chemical synthesis - the ability to make organic molecules in a controlled manner - has not diminished. Nevertheless, the increasingly complex synthetic problems being posed by nature, medicine and organic materials demand new concepts and strategies to meet these challenges. This seminar will describe new methods for selective and efficient chemical synthesis that I have developed in three different research areas: photocatalysis, hypervalent iodine chemistry, and organoboron chemistry. The generation of aryl radicals from aryl diazonium salts needs, in traditional methods, a catalytic or stoichiometric amount of a redox-active transition metal salt. Visible light can provide the required redox energy and has been considered as an ideal reagent for organic synthesis. In the first part, I will discuss the photoredox catalyzed Meerwein arylation. 1 Alkynes are ubiquitous in both naturally occurring and synthetic organic compounds. One of the most often used methods for the synthesis of alkynes consists in the addition of acetylene anions to electrophilic positions of molecules. In contrast, the reversed polarity approach, the addition of alkynes onto nucleophiles, has been less investigated, limiting the structural diversity and potential applications of this important class of compounds. In the second part, I will present electrophilic alkynylation methods using hypervalent iodine reagents.2 In the last part of the seminar, I will discuss my current research on 1,2-metalate rearrangements of boron derivatives to access substituted cyclobutane derivatives.3 This method allows for a rapid and stereoselective synthesis of Grandisol.

1 a) Hari, D. P.; Schroll, P.; König, B. J. Am. Chem. Soc. 2012, 134, 2958. b) Hari, D. P.; König, B. Angew. Chem, Int.

Ed. 2013, 52, 4734. c) Hari, D. P.; Hering, T.; König, B. Angew. Chem. Int. Ed. 2014, 53, 725.

2 a) Hari, D. P.; Waser, J. J. Am. Chem. Soc. 2016, 138, 2190. b) Hari, D. P.; Waser, J. J. Am. Chem. Soc. 2017, 139,

8420. c) Hari, D. P.; Caramenti, P.; Waser, J. Acc. Chem. Res. 2018, 51, 3212. d) Hari, D. P.; Pisella, D.; Wodrich,

M. D.; Tsymbal, A. V.; and Waser. J. Angew. Chem. Int. Ed. 2020, 10.1002/anie.202012299.

3 Hari, D. P.; Abell, J. C.; Fasano, V.; Aggarwal, V. K. J. Am. Chem. Soc. 2020, 142, 5515. b) Hari, D. P.;

Madhavachary, R.; Fasano, V.; Haire. J.; Aggarwal, V. K. J. Am. Chem. Soc.2020, submitted.