Synthesis最新文献

In this report, we have established a Ru(η⁶-C₆H₆)Cl₂ catalysed ortho-C–H activation of benzyl thioethers with alkynes under milder reaction conditions. The sulfur atom of benzyl thioethers worked as a directing group for ortho-C–H activation of benzyl thioethers. The reaction was found to tolerate a range of benzyl thioethers as well as alkynes. Moreover, the reaction is significantly influenced by the length of alkyl and aryl thioethers, with the best results being obtained with benzyl thioethers. Kinetic isotopic experiments suggest that the ortho-C–H bond-breaking is not a rate-determining step for the present reaction. In an unusual observation that has not been reported, apart from ortho-C–H activation, under the same reaction conditions, a selective debenzylative hydrothiolation was exclusively obtained with acrylates, which broadens the synthetic impact of benzyl thioethers for the preparation of mixed chalcogen ethers.

An efficient approach for the facile synthesis of phosphonylated 1,3-dihydrofuro[3,4-b]quinolines and dihydrofuro[3,4-b]pyridines is developed. Reaction proceeds by the formation of new C–P and C–O bonds affording Z-selective phosphonylated products at room temperature. Diphenylphosphine oxides and dialkyl phosphites are explicitly incorporated into the carbonyl carbon of o-alkynylaldehydes in good to excellent yields. The reaction exhibits mild conditions, broad substrate scope, and the formation of three new bonds in the presence of a silver catalyst. The mechanistic studies revealed that the reaction proceeded via an ionic pathway in a 5-exo-dig manner to give Z-selective products, which was validated by X-ray crystallographic studies. Photophysical studies of selected compounds revealed the emission maxima in the range of 455 nm.

The synthesis of silanes starting from multifunctionalized precursors often suffers from low chemoselectivity due to the similar kinetic reaction profiles, leading to the formation of difficult to separate side products. The opposite approach, which is an access based on unreactive tetraalkylsilanes as starting materials, is far less developed. Making use of the silylium-ion-initiated chemoselective halodealkylation of tetraalkylsilanes recently developed by our laboratory, an extension of this protocol, namely the direct synthesis of dihalosilanes from tetraalkylsilanes, is reported. Following a sequence of halodehydrogenation and halodealkylation, trialkylhydrosilanes can also be converted into dihalosilanes. Commercially available 1,2-dihaloethane acts as the halogen source and is involved in the generation of the catalytically active arenium ion by an S_EAr substitution of the benzene solvent. The formation of an uncommon halogen-substituted silylium ion as an intermediate is assumed, likely accounting for the need of an elevated reaction temperature.

A novel protocol for synthesizing sulfonyl fluorides from thiols in one pot is reported. Utilizing SOCl₂ and H₂O₂ as low-cost and convenient reagents allows the direct oxidative chlorination of readily available thiol derivatives to give the corresponding sulfonyl chlorides, with subsequent fluoride–chloride exchange mediated by KHF₂ giving access to the desired sulfonyl fluorides. This transformation features mild conditions, operational simplicity and high efficiency, and utilizes a broad substrate scope, including a variety of aryl, alkyl, benzyl and heteroaryl thiols.

α-Hydroxy-benzylphosphonates obtained by the Pudovik reaction of substituted benzaldehydes and dialkyl phosphites were added to the triple bond of dialkyl acetylenedicarboxylates. Optimum conditions involved a 24 hours stirring in the presence of 10% diazabicycloundecene in dichloromethane to afford the adducts as a mixture of predominant E- and a minor Z-isomers in 75–90% yields after flash chromatography. The structures of the geometrical isomers were confirmed by NOE- and ROE-measurements. Catalytic hydrogenation of the olefinic moiety of the adducts led to the diastereoisomers of corresponding saturated derivatives.