Palladium/Light Induced Radical Alkenylation and Allylation of Alkyl Iodides Using Alkenyl and Allylic Sulfones Shuhei Sumino, †,§ Misae Uno, † Hsin-Ju Huang, ‡ Yen-Ku Wu, ‡ and Ilhyong Ryu* ,†,‡ † Department of Chemistry, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan ‡ Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan * S Supporting Information ABSTRACT: Alkenylation and allylation of alkyl iodides with alkenyl and allyl sulfones, respectively, took place under Pd/ photoirradiation system. The initial alkyl radical, derived from a single electron transfer between Pd(0) and RI, underwent the title transformations. Pd(0) was regenerated through a reductive elimination of PhSO 2 PdI, which is formed by the combination of the sulfonyl radical and the palladium radical. The addition of water was effective, presumably by pushing the equilibrium through hydrolysis of PhSO 2 I. T ransition metal-catalyzed cross-coupling reactions of aryl and alkenyl halides constitute a useful means for C-C bond forming processes, and nowadays, much effort has been directed to expand the reaction scope by engaging sp 3 -hybridized alkyl halides. 1,2 A radical-based formal Mizoroki-Heck reaction of alkyl halides involves the addition of a carbon radical to a heteroatom-substituted alkene followed by a β-scission pathway (Scheme 1, eq 1). 3 In order to sustain the radical chain, the leaving radical Y • has to trigger a propagation sequence, and hexabutylditin is often used to facilitate this process (Scheme 1, eq 3). 4 Thus far, a number of alkenylating reagents has been examined in different types of radical alkenylation reactions, which include alkenyltins, 5 alkenylsulfides, 6 alkenyl sulfones, 7,8 nitroalkenes, 9 alkenylindiums, 10 alkenylgalliums, 10b alkenyl chlorides, 11 and alkenyl bromides. 12-14 Also, the radical allylation reactions following a related mechanistic pathway have been investigated (Scheme 1, eq 2). 4,6,7e,15 As part of our research program in developing Pd/light-initiated radical reactions, 16,17 we recently reported a coupling reaction of alkyl iodides and alkenyl bromides with Hanztsch ester as a reducing agent (Scheme 1, eq 4). 18 In this reaction system, the single electron transfer (SET) reaction between alkyl iodides and Pd(0) under photoirradiation is responsible for the generation of the initial alkyl radical, and Hanztsch ester serves an essential role in reducing Pd(II)IBr to Pd(0) to sustain radical chain. We envisioned that if alkenyl phenyl sulfones are employed in lieu of alkenyl bromides, the reductive elimination of Pd(II)- ISO 2 Ph would be much more facile than the case with Pd(II)IBr, 19 thus obviating the need of an additional reductant for the regeneration of Pd(0) (Scheme 1, eq 6). The same concept would promisingly be extended to the allylation sequence using allyl sulfones 7e,20,21 (Scheme 1, eq 5). Herein, we report the Pd/ light-induced synthesis of alkenylated or allylated alkanes from the corresponding sulfone precursors. We first studied the coupling reaction of iodocyclohexane 1a and phenyl styryl sulfone 2a (Table 1). When a benzene solution of 1a and 2a was irradiated by a xenon lamp in the presence of PdCl 2 , LiCl, t-BuNC, and Et 3 N, the desired product 3aa was obtained in 39% yield (Table 1, entry 1). Interestingly, the Received: December 29, 2017 Published: February 6, 2018 Scheme 1. Radical Alkenylation and Allylation of Alkyl Halides Letter pubs.acs.org/OrgLett Cite This: Org. Lett. 2018, 20, 1078-1081 © 2018 American Chemical Society 1078 DOI: 10.1021/acs.orglett.7b04050 Org. Lett. 2018, 20, 1078-1081