Phenylthio group transfer

Scheme 8. Synthesis of acetyl scopine via free-radical phenylthio group transfer...

If opportunity is given, a (thiolated) carbon atom can be transferred from a sulfur ylide to a double bond with diastereocontrol. The carbon remains on that side of the molecule which contained the sulfur initially e.g. equation 40). By similar chirality transfer, the (3-oriented phenylthio group of octalin (147) determines the -orientation of the transposed PhSCH2 unit in the reaction product (148 equation 41). The efficient formation of a quaternary center from (147) is all the more remarkable since an... 

Pasto has reported the generation of alkoxyl radical by the photo-induced ho-molytic dissociation of alkyl 4-nitrobenzenesulfenate (52]. Cekovic has examined the photolytically induced decomposition of benzenesulfenates in the presence of hexabutylditin [53]. This reaction allows selective introduction of a phenylthio group at the -position via a 1,5-hydrogen transfer. The overall reaction is an O to C transfer of a phenylthio group. This reaction has been applied for the synthesis of acetyl scopine starting from (Af-ethoxycarbonyl)nortropine benzenesulfenate (Scheme 8) [54]. The sulfenate esters are stable compounds and are easily prepared by reaction of alcohols with PhSCl/EtyN. 

Organoelement groups like the phenylthio- or diphenylarsanyl group can be removed reductively from alkyl residues very well by Raney-Nickel (Scheme 8). But the transfer of this splitting reaction to our products of anionic cycloadditions - pyrrolidine derivatives - led to difficulties because, as demonstrated in Scheme 8, in addition to the splitting of the element carbon bond ring opening or aromatization occured. 

Transfer of the phenylthio(phenylseleno) group to aldehydes and ethers... 

In DMF, with carbanions (malonates or nitronates) as nucleophiles and phenylthio or phenylsulphonyl leaving groups, a chain radical substitution takes place at an allylic carbon. This SRN1 like reaction was found to be activated by visible light, the only possible absorbing species being a charge transfer complex between the anion and the substrate [218]. 

A series of polymerizations were performed to determine the effect of changing the diphenyl sulfone central group of the bis(phenoxy) and bis(phenylthio) monomers to a pentanedioxy group. The polymers obtained from methyl-substituted 1,5-bis(phenoxy)pentane contained structural units derived from proton transfer reactions [214]. Thus diphenyl methane, 1,2-diphenyl ethane, and benzyl chloride units were detected (Fig. 52). 

The photoreduction of the above dye, 5,7-diiodo-3-pentoxy-9-fluorenone, in the presence of (phenylthio)-acetic acid and its tetrabutylammonium salt occurs via a photoinduced electron transfer process. On the basis of the known photochemistry of sulfur-containing aromatic carboxylic acids, it is postulated that the existence of the carboxyl group in an ionic form allows a rapid decarboxylation, yielding a neutral very reactive a-alkylthio-type radical (R-S-CH2 ). 

Piers and Morton have reported that lithium (phenylthio)(trimethyl-stannyOcuprate smoothly transfers one trimethylstannyl group to a,/3-acetylenic esters in a conjugate sense to give /3-trimethylstannyl-a,/3-olefinic esters. Importantly, products of almost exclusive E- or Z-geometry are formed under conditions of kinetic or thermodynamic control. Partial reduction followed by Wittig... 

---