212. Dithiols. Part XXI. Dithiols from cyclic trithiocarbonates

Abstract

The reductive fission of cyclic trithiocarbonates provides a useful method for the synthesis of dithiols, and is applicable to the preparation of vicinal disecondary thiols which may not be readily accessible by other routes. The method offers particular advantages in the carbohydrate field, and has been used to synthesise three dithiols and one tetrathiol related to the hexitols.Although cyclopentene oxide does not give a trithiocarbonate with xanthate, cyclopentene sulphide readily gives tmns-1,2-(thiocarbonyldithio)cyclopentane (XXX), a compound containing two trans-fused five-membered rings. Reasons for this difference in behaviour are discussed.ALKALINE hydrolysis of cyclic trithiocarbonates is reported l p 2 to give only poor yields of dithiols. It is known, h~w e v e r ,~ that thiols can be prepared very satisfactorily by the reductive fission of xanthates with lithium aluminium hydride, and this procedure should evidently be applicable to trithiocarbonates, though the only report is of the small-scale reduction of the unsaturated cyclic trithiocarbonate (I) to give ethane-l,2-dithiol in unspecified yield.In some trial experiments, ethane-1,2-, propane-1,3-, propane-1,2-, and cyclohexanetrans-lJ2-dithiol were obtained by reduction of the corresponding trithiocarbonates with lithium aluminium hydride in yields of 86, 37, 75, and goyo, respectively; for the last two compounds the reported The configuration of the cyclohexane-trans-l,2-dithiol (IV) was not specified by the earlier workers, but since the reductive fission does not affect any asymmetric centre it must be the same as that of the trithiocarbonate (111) from which it is derived; the latter is trans, since it is formed through the intermediate episulphide (II).? The dithiol obtained by fission of the episulphide (11) with potassium hydrogen sulphide must also be trans. Although cyclohexane-trans-l,2-diol does not condense with aldehydes or ketones under normal condition~,~ the dithiol (IV) readily gave the crystalline isopropylidene derivative (V) on treatment with acetone and a trace of sulphuric acid at room temperature; this is no doubt due to the great stability of the resulting dithiolan system. The corresponding benzylidene and piperonylidene derivatives have already been described,2 but without comment.Conventional methods for the synthesis of simple thiols often fail when attempts are made to prepare vicinal dithiols in which both groups are secondary. Thus many vicinal disecondary halides undergo dehalogenation to the olefin, rather than substitution, on yields by alkaline hydrolysis are 26 and 14%.* Part XX, Fitt and Owen, J., 1957, 2250. t The mechanism of the formation of cyclic trithiocarbonates is outlined in the preceding paper.5

Synthesis of Titanium(IV) and Zirconium(IV) Complexes with an [OSSO]-Type Bis(phenolate) Ligand Bearing a trans-Cyclohexane-1,2-diyl Ring and 1-Hexene Polymerization

“…Zirconium and Titanium Chelating Alkoxide Complexes 14 b = 33.704(2) Å, c = 11.0361 (7) Å, β = 109.3670(10)°, V = 3482.9(4) Å 3 , Z = 4, D calcd = 1.116 g cm À3 , R1 (I > 2σ(I)) = 0.0661 and wR2 (all data) = 0.1864 for 6478 reflections and 446 parameters, GOF = 1.094. Crystallographic data and details of refinement for (Δ*,S*,S*)-9: C 87 H 143 O 8 S 4 Ti 2 ((C 42 H 68 O 4 S 2 Ti) 2 3 0.5C 6 H 14 ), MW = 1541.05, monoclinic, space group P2 1 /n, a = 19.3273(17) Å, b = 13.9791 (11) Å, c = 34.816(3) Å, β = 104.7800(10)°, V = 9095.3(13) Å 3 , Z = 4, D calcd = 1.125 g cm À3 , R1 (I > 2σ(I)) = 0.0452 and wR2 (all data) = 0.1073 for 16 868 reflections and 943 parameters, GOF = 1.094.…”

Base initiated depolymerization of polycarbonates to epoxide and carbon dioxide co-monomers: a computational study

“…29 Additionally, trans-fused five-membered cyclic rings are unstable relative to cis-fused isomers due to their strained geometries (Table 3), and this statement is generally true. 32 Replacing oxygen with sulfur leads to less strain due to the C-S bond (∼1.83 Å) being longer than C-O bonds (1.44 Å), and trans-cyclopentene trithiocarbonate is well known. 32,33 To explain the formation of cis-cyclopentene carbonate, the polymeric alkoxide is rapidly converted to carbonate in the presence of carbon dioxide (e.g.…”

“…32 Replacing oxygen with sulfur leads to less strain due to the C-S bond (∼1.83 Å) being longer than C-O bonds (1.44 Å), and trans-cyclopentene trithiocarbonate is well known. 32,33 To explain the formation of cis-cyclopentene carbonate, the polymeric alkoxide is rapidly converted to carbonate in the presence of carbon dioxide (e.g. from epoxide-forming reactions).…”

Dithiols. Part XXIV. Proof of the epoxide chirality in 2,3-epoxypropyl β-D-glucopyranoside by correlation with (R)-2,3-thiocarbonyldithiopropanol

“…(chloroform) to give the trithiocarbonate (0.46 g) as a yellow oil, [aIDa1 4111" (c 1.1), v , , 1740 cm-l, T 4-5-6.9 (12H, m) and 7. 90,7.93,7.96,and 7.98 (12H,4s,4 OAc) (Found: C,43.75;H,5.0;S,19.15. C,,H2,010S3 requires C,43.5;H,4.9;S,19.4%).…”

“…90,7.93,7.96,and 7.98 (12H,4s,4 OAc) (Found: C,43.75;H,5.0;S,19.15. C,,H2,010S3 requires C,43.5;H,4.9;S,19.4%).…”