Aryl/vinyl thioethers containing C(sp 2)-S bonds are prevalent in biologically relevant molecules and compounds with other potential applications. Around the past decade, rapid progress has taken place in the research area of C(sp 2)-S construction, and a large number of efficient new catalytic systems as well as structurally versatile substrates have been identified for such reactions, which significantly enriched the content of the synthetic methodologies on C(sp 2)-S bond formation. This review introduces mainly the research advances on transition metal-free C(sp 2)-S bond forming reaction by means of C(sp 2)-H bond functionalization over the period of 2001～2016. Keywords transition metal-free; C(sp 2)-H bond; (Hetero)aryl; vinyl; C(sp 2)-S bond formation

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Combretastatins-A4 (CA-4) is a natural product with extraordinary anticancer activity, which was isolated from the South African Tree-Combretum caffrum. However, the cis-isomer exhibits strong antitubulin activity only, but the cis-isomer tends to isomerize the inactive trans-isomer. In this paper, an additional pyrrolidone ring system was used to replace the cis double bond to arrest the cis-conformation. Thus, four new compounds of 3,4-diaryl pyrrolediones and 3,4-diaryl pyrrolones as CA-4 analogues were synthesized from the starting materials 3,4-dimethoxyacetophenone or 3-fluoro-4-methoxy acetophenone, via a four steps reaction, α-bromination, improved Gabriel reaction, condensation with 3,4,5-trimethoxyphenylacetic acid and intramolecular cyclization under air or nitrogen. The structures of these new compounds were confirmed by 1 H NMR, 13 C NMR, ESI-MS and elemental analysis. The in vitro antitumor activities of CA-4 analogues against HL-60, SMMC-7721 and A549 human gastric cancer cell lines were tested using colorimetric MTT assay. The preliminary result indicates that 3-(3-fluoro-4-methoxyphenyl)-4-(3,4,5-trimethoxyphenyl)pyrrole-2,5-dione (1b) shows significant antitumor activity (0.03～ 0.05 μmol•L -1 ), which is closely to the natural CA-4.