A New Cyclisation of Sulfenylated Dimethyl Sulfoxide and Thiosemicarbazone Adducts using Thionyl Chloride†

Novel Annulation of the Thiete Ring on Imidazole Nucleus and LiI-Catalysed Expansion of the Thiete Ring with Carbon Disulfide

“…Thus, to a solution of 3 (10.0 mmol) in anhyd t-BuOH (20 mL) was added a solution of 4 (10.0 mmol) in anhyd t-BuOH (10 mL) at r.t. and the reaction mixture was refluxed for 3 h. The solvent was evaporated under reduced pressure and the residue was recrystallised from EtOH to give a mixture of diastereomers (>97:<3; in the crude isolates, the ratio was >93:<7 as determined by 1 H NMR spectroscopy) which was again recrystallised from EtOH to obtain an analytical sample of a single diastereomer 5 ( Table 1). On the basis of 1 H NMR spectra and published data, 6,9,[11][12][13] the adducts 5a and 5e were assigned the erythro (syn) stereochemistry, as their 1 H NMR spectra exhibit a coupling constant, J NCH,SCH = 5 Hz, which is smaller than that of the very minor (<3%) diastereomer (threo or anti), J NCH,SCH = 10 Hz. Adducts 5a and 5e were refluxed with equimolar amounts of t-BuONa in t-BuOH for 4 h to give the corresponding compounds 6a and 6e in 85% and 93% yield, respectively.…”

“…Prompted by the unexplored chemistry and bioactivity of thieto-imidazoles 6 and in pursuing our work on new synthetic routes involving sulfur-and phosphorus-based leaving groups, [6][7][8][9] we have devised the synthesis of 6 and their ring expansion to 7. Having in view a long history of applications of imidazoles in pharmaceutical and agrochemical areas, we chose to annulate the thiete ring on the biologically versatile imidazole nucleus.…”

An Expeditious Solvent Free Synthesis of Functionalised Thietanes by Nucleophile-Induced Cyclisation ofO,O-DiethylS-(1,3-Diaryl-3-oxopropyl) Phosphorodithioates

“…Prompted by the above consideration and in continuation of our work on heterocyclisations involving sulfur-and phosphorus-based leaving groups, [2][3][4][5] we have devised the present nucleophile-induced cyclisation of Michael adducts 3 to functionalised thietanes 5 which are not accessible through any one of the known synthetic routes for thietanes. 1,2 After some preliminary experimentation, it was found that the envisaged cyclisation (3®5) was successful with carbon and sulfur nucleophiles 4 under microwave irradiation in the solid phase (Scheme 1).…”