Copper-Catalyzed Cycloaddition of Heterobicyclic Alkenes with Diaryl Disulfides to Synthesize Dihydrobenzo[b]thiophene Derivatives

Abstract

A novel copper-catalyzed cycloaddition of diaryl disulfides to heterobicyclic alkenes has been developed. The CS and CC bonds can be formed simultaneously on the CC bond of the olefins via a single-step cycloaddition to afford a series of 2,3-dihydrobenzo­[b]­thiophene derivatives. This reaction exhibits excellent diastereoselectivity and relatively broad substrate scope. Various functional groups attached to the substrates are tolerated in this protocol to give the corresponding exo adducts in moderate yields.

Synthesis of Dithioacetals through Iodine-Promoted Insertion Reactions of Vinylsilane to Disulfides and its Application to Diselenoacetalization

“…As an initial trial, when di-p-tolyl disulfide (0.5 mmol) and vinyltrimethylsilane (1.5 mmol) were treated with I2 (0.3 mmol) and NaF (1.5 mmol) in a toluene solution (1 mL) at 80˚C, the desired dithioacetal derivative, bis(p-tolylthio)methane (1), was achieved in a 46% GC yield (entry 1). Unlike the previous 1,2-addition of disulfides to vinyltrimethylsilane with a ruthenium complex, 8 1 H and 13 C NMR measurements exhibit a geminal structure of two sulfur atoms at the 1,1'-position. When using KF instead of NaF, however, the chemical yield was improved to isolate dithioacetal 1 in a 73% yield (entry 2).…”

“…1 H NMR (500 MHz, CDCl3): d = 7.25-7.49 (m, 10 H, C6H5), 4.54 (q, J = 6.8 Hz, 1 H, CH), 1.61 (d J = 7.0 Hz, 3 H, CH3). 13 C NMR (125 MHz, CDCl3): d = 134.1, 132.9, 128.9, 127.8, 52.2, 22.8.…”

“…CH 3 CN and CH 2 Cl 2 were dried over CaCl 2 and were then freshly distilled over CaH 2 . 1 H NMR spectra were measured at 500 MHz and 13 C NMR spectra were measured at 125 MHz. Chemical shifts in the 1 H and 13 C NMR spectra reported in ppm relative to residual solvent peaks such as those of chloroform ( 7.26 for 1 H, and  77.0 for 13 C) or the internal reference TMS ( 0.00 for 1 H).…”

“…13 C NMR (CDCl3, 125 MHz): d = 138.0, 133.5, 130.3, 129.6, 52.8, 22.6, 21.2. MS (EI): m/z (%) = 274 (M + , 29), 151 (100).…”

“…On the other hand, unlike a 1,2-addition mode shown above, there are other examples, which show that the reaction of diaryl disulfides with alkenes in the presence of Cu(OTf) 2 and I 2 leads to the preparation of aryl vinyl sulfide derivatives (Scheme 1d), 11 and indium(I) iodide promotes the addition of disulfides to styrenes in the presence of zinc chloride to afford linear sulfide derivative (Scheme 1e), 12 while the copper(II)-catalyzed sulfidation of diaryl disulfide with benzonorbornadiene has yielded sulfur-containing heterocycles (Scheme 1f). 13 In order to further expand the facile preparation of these significant disulfidation derivatives, the development of different addition modes of disulfides toward alkenes is in great demand.…”