Thiadecalins

The preference for the axial position in unhindered thiane-1-oxides has been known for some time. The spectra of the cis and trans isomers of the 2-, 3- and 4-methyl thiane-1-oxides, 169-171, were also measured. It was concluded from the 13C chemical shifts that the methyl groups preferred the equatorial positions. A comparison of the 170 chemical shifts obtained for sulfoxides 169-174 with those obtained for the cis and tram sulfoxide isomers of trans- 1-thiadecalin, 175 and 176, was consistent with this proposal. Sulfoxide 175 with the S=0 axial gave a shift about 17 ppm upfield from that of its equatorial isomer 176. For sulfoxides 169-174, the conformers proposed to have the S=0 axial gave shifts that were upfield from those of the supposed equatorial conformers. For tram-3, (rans-5-dimethylthiane-1 -oxide (177) with the oxygen axial, the 170 signal was 21 ppm upfield from the signal observed for the equatorial oxygen in cis-3, cis-5-dimethylthiane-l-oxide (178). 

The nomenclature of the family of compounds to be discussed below has for long been the cause of much confusion. The systematic name for a six-membered ring containing one sulfur atom is thiin, but Chemical Abstracts uses the name thiopyran, while many earlier publications have used the replacement nomenclature thiapyran (which is strictly inaccurate as thia implies replacement of carbon, rather than oxygen, by sulfur). Throughout this chapter the terms thiopyran and thiin will be used interchangeably, while thiadecalin nomenclature will be found convenient for the perhydrobenzothiopyran systems. 

Some heteropolycycloalkanes, e.g. indolizidine, quinolizidine, tropane, and decahydro-quinoline, are parent skeletons of alkaloids. Carbon-13 shifts of these and other parent polycycloalkanes [408] (Tables 4.64 and 4.65) are predominantly determined by heteroatom electronegativity, ring size, stereoisomerism, and dynamic effects. Aza- and thiade-calins are representative examples (Table 4.64). As described for cis- and trans-decalin (Section 4.1.3), carbon nuclei in the cis isomers of aza- and thiadecalins are shielded... 

Rooney, R.P., and Evans, S.A., Jr., Carbon-13 nuclear magnetic resonance spectra of trans-l-thiadecalin, trans-1,4-dithiadecalin, trans-l,4-oxathiadecalin, and the corresponding sulfoxides and sulfones,. /. Org. Chem., 45, 180, 1980. 

The partially reduced thiopyrans are 3,4-dihydro-2//-thiopyran 20 and 3,6-dihydro-2//-thiopyran 21 and the fully reduced compound is tetrahydrothiopyran or thiane 22. The benzologues are 3,4-di hydro-2//-1 -benzothiopy ran or thiochroman 23 and 3,4-dihydro-l//-2-benzothiopyran or isothiochroman 24. The fully saturated derivatives of 23 and 24 are known as thiadecalin and isothiadecalin, respectively. 

Desulfurization of the /ra r-thiadecalin-8-one 399 with Raney nickel gives 3-propylcyclohexanone (Equation 106) <2000TL2279> and thiochroman-4-one is efficiently desulfurized to propiophenone on heating with metallic sodium in mesitylene after initial separation of the enolate (Equation 107) <1998TL2671>. 

The trans-fused 1-thiadecalin 462 is the major product from the radical cyclisation of 2-(3-iodopropylthio)cyclohex-2-enone a spiro-linked tetrahydrothiophene arising from 5-endo cyclization is also formed. The trans-iuscd benzo-[fjthiadecalin 463 is formed almost exclusively from the analogous 2-iodophenyl derivative (Equations 151 and 152) <2000TL2279>. 

Thiopyrylium salts can be also reduced by zinc in hydrochloric acid. Thus cation 77 (R = R = Ph, = 2) by treatment with Zn/HCl gave a mixture of 6//-thiopyran 269, 4//-thiopyran 270, and the corresponding thiadecaline [71KGS(S)85]. 

Asymmetric Michael Addition. An intramolecular Michael reaction catalyzed by (S)-proline leads to the chiral thiadecalin (9) and thiahydrindan (11) and (12). Enone (8) undergoes cyclization in the presence of (S)-proline to give exclusively the trans isomer (9) (eq 4). The thiahydrindandions (11) and (12) are obtained from (10) as a 1 1 mixture of the cis and trans isomers (eq 5). 

Thiochromans and thiochroman 1,1-dioxides are readily prepared from the corresponding thiochroman-4-one by catalytic hydrogenation in acetic acid/perchloric acid or via the Wolff-Kishner and Clemensen methods. Thermal decomposition of 21 produced thiochroman in 85% yield. Thiochroman and isothiochroman occur in petroleum, and the completely saturated analog of the former (1-thiadecalin) was obtained from propenyl 1-cyclohexenyl ketones in the presence of hydrogen sulfide and sodium acetate in ethanol. 

This transannular addition of a-sulfinyl carbanions to nonactivated double bonds is utilized as the key step in a synthesis of trans-1-thiadecalin (70) in enantiomerically pure form. The required ( )-thiacy-clodec-4-ene 5-oxide (66a,b) was prepared via several steps frtm (/ ,/ )-l,6-dibromo-3,4-hexanediol. Upon treatment with butyllithium, a 4 1 mixture of isomeric sulfoxides (66a and 66b) undergoes smooth cyclizadon to give a mixture of isomeric bicyclic sulfoxides (67a and 67b) in the same 4 1 ratio as the starting material, suggesting that the cyclizadon is essentially stereospecific. The major isomer (67a) is reduced with PCb to a sulfide (68) from which the desired (70) is derived via a thiaoctaline (69 heme 16). 

Disubstituted tetrahydrothiopyrans, synthesis of 83CRV379. Tetrahydrothiopyran-4-one and syntheses based on 85AKZ166. Thiadecalins and 2-thiabicyclo [4.3.0]nonanes, synthesis and reactivity of ... 

Indeed, reactions of 5,6-dihydro-2,3-dimethyl-1,4-dioxin, -1,4-oxathiin, and -1,4-dithiin with bromine in the presence of 1,2-ethanediol, 2-thiolethanol, and 1,2-ethanedithiol, respectively, afforded, in most cases, high yields of the corresponding oxa- and thiadecalins as cis isomers only XiACS4l0>. 

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