New generation of thiocarbonyl ylide and its 1,3-cycloaddition leading to tetrahydrothiophene derivatives

Biotin: A Timeless Challenge for Total Synthesis

“…117 The synthesis basically involves three stages. In the first stage, the thiophane nucleus of biotin is constructed via a 1,3-cycloaddition process between maleic anhydride and a thiocarbonyl ylide that is generated from a sulfide according to Achiwa et al 118 Subsequent methanolysis of 263 that was obtained with excellent stereoselectivity, led to acid 264, at which point the shown all-cis configuration was determined. In the following stage of the synthesis, acid 264 is transformed into 267 through two stepwise Curtius rearrangement sequences, to yield 265 and 266, followed by the construction of the urea ring in the usual way.…”

Thiocarbonyl ylides. VI. New generation of thiocarbonyl ylides from organosilicon compounds containing sulfur and their 1,3-cycloadditions.

“…As mentioned in the preliminary communication, 3) we have found a convenient method for generating thiocarbonyl ylides and for carrying out their 1,3-dipolar cycloaddition leading to tetrahydrothiophene derivatives by using organosilicon compounds. In this paper we present the details of this work.…”

“…We designed an organosilicon compound containing sulfur, bromo(trimethylsilyl)methyl trimethylsilylmethyl sulfide (2a), which was easily prepared by bromination of bis(trimethylsilylmethyl) sulfide (1a) with N-bromosuccinimide (NBS). After several preliminary experiments, thermolysis of 2a in N,N-dimethylformamide 2a 3 (DMF) has been found to afford trimethylsilylthioaldehyde S-methylide (3). The results of initial experiments on the 1,3-cycloaddition of 3 to several symmetrical dipolarophiles are shown in Table I phenyl sulfide with a dipolarophile under similar conditions, the silyl group at the carbon without bromine seems to play a role as a leaving group.…”