A convenient preparation of mixed allylic and allenic thiosulfinates

From Allylic Sulfoxides to Allylic Sulfenates: Fifty Years of a Never-Ending [2,3]-Sigmatropic Rearrangement

“…Braverman et al found that bis-propargylic dialkoxy disulfides 490 are stable in solution only at low temperature (−18 °C), whereas, upon reflux in CHCl 3 , they undergo a double sulfenate–sulfoxide rearrangement, providing bis-allenyl sulfoxide 491 (Scheme ), which dissociates into two allenyl sulfinyl radicals 492 that recombine through the oxygen atom (R 1 = H) to give 493 , which undergoes consecutive [3,3]-sigmatropic rearrangement and intramolecular [2 + 2]-cycloaddition to yield 496 , a dithiabicyclo [3.1.1] derivative containing the sulfur core of zwiebelane (>99%; R 1 = H, R = Me). Also, for sterically demanding R groups (R = t -Bu), nucleophilic addition of sulfur onto the allene produces 495 , which evolves through intramolecular 1,3-dipolar cycloaddition to oxadithiobicyclo [2.2.1] 497 , obtained as a 71:29 mixture of diastereomers . Alternatively, recombination of 492 through the sulfur atom takes place mainly for R = H, generating a mixture of regioisomeric thiosulfonates 500 and 501 (R 1 = TMS, 78:22; R 1 = Et, 45:55). , …”

“…Also, for sterically demanding R groups (R = t-Bu), nucleophilic addition of sulfur onto the allene produces 495, which evolves through intramolecular 1,3-dipolar cycloaddition to oxadithiobicyclo [2.2.1] 497, obtained as a 71:29 mixture of diastereomers. 297 Alternatively, recombination of 492 through the sulfur atom takes place mainly for R = H, generating a mixture of regioisomeric thiosulfonates 500 and 501 (R 1 = TMS, 78:22; R 1 = Et, 45:55). 298,299 The sulfenate−sulfoxide rearrangement is also useful for transforming [2.2]paracyclophanes (Scheme 85).…”

Facile Syntheses of Allylic Allenethiosulfinates and -sulfonates, and of β-Iodo α,β-Unsaturated γ-Sultines

“…Within the framework of our ongoing studies of the chemistry of novel organosulfur compounds, we recently reported the first successful synthesis and characterization of propargyloxy and allyloxy chlorodisulfides (ROSSCl) . While these compounds were found to be reasonably stable in chloroform solution at −18 °C, they decomposed rapidly when isolated at room temperature.…”

“…While these compounds were found to be reasonably stable in chloroform solution at −18 °C, they decomposed rapidly when isolated at room temperature. However, the synthetic potential of α-alkyl-substituted representatives of these structures was demonstrated by their 1,4-addition to the nucleophilic diene 2,3-dimethyl-1,3-butadiene and subsequent spontaneous [2,3]-sigmatropic rearrangement to substituted allyl allenethiosulfinates and substituted allyl 2-propene-1-thiosulfinates, respectively . Such compounds are derivatives of allicin (allyl 2-propene-1-thiosulfinate), which has been isolated from common garlic, Allium sativum , and has been found to have remarkable medicinal properties .…”

“…To examine the regioselectivity of the addition of alkoxy chlorodisulfides to unsymmetrical 1,3-dienes, we reacted α-methylpropargyloxy chlorodisulfide, 1a , with isoprene at room temperature in the manner described for the reaction with 2,3-dimethyl-1,3-butadiene (see Scheme ) . As in the latter case, the product isolated was an S -allyl allenethiosulfinate ester, specifically 3a (74% yield), which was formed by 1,4-addition of 1a to the diene, followed by a [2,3]-sigmatropic rearrangement of the thiosulfoxylate 2a .…”