A facile α-arylation of nitriles has been developed by simply introducing TfO and DABCO to the mixture of nitriles and aryl sulfoxides. The transformation consists of two sequential steps: (i) TfO-initiated electrophilic assembly and and (ii) DABCO-triggered rearrangement. Each step can be tuned independently by changing the temperature and/or base. This adjustability allows the method to accommodate a wide range of substrates. Notable features of this new protocol include remarkable efficiency (20 min, -30 °C), exclusive regioselectivity, and high functional group compatibility, which can be challenging issues in traditional approaches. NMR studies not only identified a unique, highly unstable sulfonium imine complex but also demonstrated the importance of temperature in the formation and manipulation of this key intermediate. Further DFT calculations suggested that an electrophilic assembly, followed by removal of HOTf (by base), and finally [3,3]-sigmatropic rearrangement are three key stages in the reaction. The versatile transformability of the products and easy scalability of this reaction are also exhibited here.
We report a simple protocol for (ethoxycarbonyl)difluoromethylthiolation of nucleophilic compounds using a difluoroalkyl sulfonium salt which can be in situ prepared via Tf2O triggered electrophilic activation of a benzyl difluoroalkyl sulfoxide. With the protocol, difluoroalkylthiolated arenes, heteroarenes and α-difluoroalkylthiolated carbonyl compounds etc. were obtained smoothly with good to excellent yields. Merits of the reaction include the readily available difluoroalkylthiolation reagent and substrates, mild conditions, and excellent regioselectivity.
The title compound was previously prepared by Cui et al. (2013), and its derivatives were synthesized by Yang & Cheng (2001) and Whelligan et al. (2010). We present here the crystal structure of the compound (Fig. 1). In the molecule, the conformation of the dioxaborolane ring is similar to half chair, and the butyl group adopts an extended conformation with a C10-C11-C12-C13 torsion angle = 179.52 (19) . No hydrogen bonding is observed in the crystal.
Synthesis and crystallizationTo a solution of 1-(hex-1-yn-1-yloxy)-3-methylbenzene (94 mg, 0.5 mmol) in 2.0 ml of tetrahydrofuran (THF) was added neat 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (HBpin) (71 mg, 0.55 mmol) under nitrogen atmosphere. After stirring at room temperature for 1.5 h, the reaction mixture was concentrated and purified by on silica gel (petroleum ether/EtOAc = 60/1).
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