Photocatalyst-free visible light driven synthesis of (E)-vinyl sulfones from cinnamic acids and arylazo sulfones Ruchi Chawla a , Shefali Jaiswal a , P.K. Dutta a , Lal Dhar S. Yadav b,⇑ a Polymer Research Laboratory, Department of Chemistry, Motilal Nehru National Institute of Technology Allahabad, Prayagraj 211004, India b Green Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad 211 002, India article info Article history: Received 13 February 2020 Revised 30 March 2020 Accepted 1 April 2020 Available online xxxx Keywords: Cinnamic acids Photocatalyst-free Vinyl sulfones Arylazo sulfones abstract A photocatalyst-free visible light mediated decarboxylative sulfono functionalization protocol has been explored for the synthesis of (E)-vinyl sulfones from cinnamic acids and bench-stable arylazo sulfones. The latter have been utilized as sulfonyl radical precursors under blue LED irradiation along with Cs 2 CO 3 , air and KI to obtain the vinyl aryl sulfones as well as vinyl alkyl sulfones in moderate to excellent yields. Besides the non-photocatalytic conditions, high ecosustainability, low cost, ease of operation and access to vinyl alkyl sulfones are certain indispensable traits of the developed method. Ó 2020 Elsevier Ltd. All rights reserved. Visible light driven decarboxylative cross-coupling reactions have transpired as an extremely resourceful tool for the construc- tion of CAC and C-heteroatom bonds over the last few years [1]. Using these reactions, formation of new bonds takes place in a highly ecosustainable manner owing to the readily available start- ing materials and the innocuous and easily removable by-product (CO 2 ). Moreover, milder reaction conditions, higher efficiency, greater selectivity and exceptional functional group compatibility add to the credentials of this strategy. In general, these visible light mediated transformations are brought about by a photocatalyst (polypyridyl metal complexes or organic dyes) [2]. An attractive alternative to these expensive or degradable catalysts can be the use of a photoactive substrate or reagent which precludes the use of any external photosensitizer. The concept is highly appeal- ing but the number of reports on such photocatalyst-free visible light mediated decarboxylative cross-coupling reactions is limited [1,3] which allows ample room for the development of novel pro- tocols based on this approach. Vinyl sulfones, as a class of organosulfur compounds, are inter- esting targets of synthesis due to their potential biological activity [4] and versatile synthetic utility [5]. Among the various methods available for their synthesis, the decarboxylative sulfonylation of cinnamic acids is a simple and direct method for their synthesis [6]. This synthetic approach has drawn significant attention over the last few years and the target molecules have been synthesized under both transition-metal catalysed [6a-d] and transition-metal- free conditions [6e-m]. However, most of these methods suffer from drawbacks, viz. use of expensive metal catalysts, elevated https://doi.org/10.1016/j.tetlet.2020.151898 0040-4039/Ó 2020 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: ruchi@mnnit.ac.in (R. Chawla), ldsyadav@hotmail.com (L.D.S. Yadav). Ar COOH S O O NHNH 2 Ar' Ar S Ar' O O eosin Y, KI, Cs 2 CO 3 O 2 , DMF/H 2 O, h, rt Ref. 6l Ar' S O O OAr Ar Ar' S Ar O Cs 2 CO 3 , rt, DMA, Ar, Blue LEDs electron donor-acceptor complex approach Ref. 3c Ar COOH Ar S Ar' O O Merrifield resin supported Rose Bengal ammonium salt (5 mol%) TBHP (2 equiv.), DMSO/H 2 O, h, rt Ref. 6m Ar COOH S S Ar' Ar S Ar' O Ru (phen) 3 (PF 6 ) 2 (3 mol%) Cs 2 CO 3 (2 equiv.), DMSO O 2 , blue LED, rt Ref. 6d Ar'SO 2 Na Ar' Ar COOH Ar'N 2 SO 2 R Ar S R O O KI, Cs 2 CO 3 , open flask 1,4-dioxane/H 2 O, blue LEDs, rt Our work: COOH R= alkyl, aryl O O Previous work: a) b) c) d) e) photoactive reagent photocatalyst-free Scheme 1. Visible light mediated synthesis of vinyl sulfones from cinnamic acids. Tetrahedron Letters xxx (xxxx) xxx Contents lists available at ScienceDirect Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet Please cite this article as: R. Chawla, S. Jaiswal, P. K. Dutta et al., Photocatalyst-free visible light driven synthesis of (E)-vinyl sulfones from cinnamic acids and arylazo sulfones, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2020.151898