Does a 1,4-hydrogen shift occur in .beta.-(alkylthio)ethyl radicals?

Abstract

The polar fractions decomposed rapidly and could not be studied satisfactorily. Photooxygenation of 1 g of 3b in acetone at 10 °C for 1 h gave 418 mg (36%) and photooxygenation of 1.5 g of 3b in acetone at 78 °C gave 279 mg (31% based on recovered diene) at 19b. l-Methyl-4,5-dihydronaphtho[2,l-b]furan (20a). Reaction of 0.2 g of 19a in 15 mL of THF with 0.4 g of FeS04-7H20 in 20 mL of H20 at room temperature for 2 h followed by the usual workup and chromatography over 20 g of silica gel gave 0.16 g (88%) of 20a:

The β-sulfur substituent effect in radical reactions. Chlorine-atom abstraction from alkyl 2-chloroethyl sulfides, hydrogen-atom abstraction from dialkyl sulfides and the question of possible 1,4-hydrogen-atom transfer in β-alkylthioethyl radicals

“…1b), presumably as a consequence of restricted rotation about the S-CH 2 bond or 3a, which is quite similar to that reproduced in ref. 11. We confirmed the report 11 that at lower temperatures than this the spectrum ascribed to the 'rearranged' radical was relatively stronger.…”

“…11. We confirmed the report 11 that at lower temperatures than this the spectrum ascribed to the 'rearranged' radical was relatively stronger. Conversely, at temperatures above ca.…”

“…The 'other' radical detected by Casarini et al 11 during the UV photolysis of MeSSMe in the presence of ethene (Fig. 3a) is not the isomeric radical 15, but is almost certainly the αalkylthioalkyl radical 17.…”

“…Casarini et al 11 reported that UV photolysis of dimethyl disulfide in a mixture of ethene and cyclopropane as solvent affords the EPR spectrum of 10 [eqns. (9) and ( 10)], along with that of another radical presumed to be 15.…”

“…However, in our hands, UV irradiation of cyclopropane solutions containing 21 and Me 3 SnSnMe 3 , with or without added DTBP, did not afford the spectrum of 20 (or of a radical with similar EPR parameters) in addition to that of 19, which was relatively strong in the presence of DTBP. Authentic 20 was generated by photolysis of DTBP in the presence of diethyl sulfide, as described previously; 28 competitive abstraction from the methyl groups was not observed at 200 K ([20]/[19] ≥ 15).|| When we repeated the photolysis of diethyl disulfide in the presence of ethene, as described by Casarini et al, 11 we could not detect the spectrum of the rearranged radical 20 alongside that of the primary adduct 19, although some weak lines which might derive from EtSCH 2 CH 2 SC ˙HMe, were indeed present. ** In any event, when DTBP was photolysed in the presence of 2-chloroethyl ethyl sulfide 22 and TMBB between 180 and 240 K, in experiments similar to those carried out with the methyl analogue 7, no trace of the radical 20 or of a similar alkylthiomethyl radical could be detected alongside the radical 19.…”