Thiophenes 2-alkylthio- from

Thiophene-2-carboxylic acid, 5-(alkylthio)-thiophenes from, 4, 892 Thiophene-2-carboxylic acid, 5-amino-reactions, 4, 810... 

Photoelectron spectroscopy is an efficient tool for the gas-phase characterization of various elusive compounds <1989CSR317>. It has also been used to investigate the products formed on flash vacuum pyrolysis of alkylthio derivatives of Meldrum s acid <1991JOC3445>. The PESs of the thiophen-3(2//)-ones formed were similar to authentic samples from which it is apparent that no keto-enol tautomerism occurred in the gas phase and that only the keto tautomers are formed in the gas phase. 

Alkoxy- and alkylthio-substituted aminothienopyrimidines 94 were prepared by cyclization of the corresponding isoureas and isothioureas 95. Isoureas are generated in situ from thiophenes 30 with cyanates in the presence of acids (1984INDP151496). Isothioureas are produced by alkylation of thioureas 33 (1991GEP287503). 

Polythiophene deposition from oxidation of thiophene often results in poor materials due to overoxidation at the high potential required. The best results are obtained with 3-methylthiophene and bithiophene which are more easily oxidized [81-3]. The degree of polymerization is some hundreds for poly(3-alkylthio-phenes) [84] and 10-35 for polythiophene [85]. The polymer is mainly coupled at the 2 and 5 positions (Figure 4.5) [86]. 

A new thiophen synthesis is based on deprotonation and cyclization of the resultant carbanion (65) of a keten dimethylthioacetal. Other applications of cr-(phenylthio)- or cr-(alkylthio)-alkyl-lithiums include preparations of disparlure (the sex pheromone of the gypsy moth) and other chiral epoxides,of an anti-peptic-ulcer diterpene from Croton sublyratus, of carbene-thiometal chelates through reaction with fCr(CO)gl or fW(CO)jl, of olefins via )ff-hydroxy-sulphides, and of Michael adducts of enones. In other work, the chiral solvent l,4-dimethylamino-2,3-dimethoxybutane is employed in enantioselective addition reactions of cr-thio-carbanions with ketones and Michael acceptors. a,P -Elimination of cr-thio-carbanions such as (66) provides a useful synthesis of olefins, and a 2-(lithiomethylthio)-A -oxazoline (67) has been used to prepare a C-labelled thiiran for a microwave study of the valence tautomerism of allene episulphide. ... 

Continuing interest in rotation barriers about single bonds in acyclic radicals, as determined by the interpretation of e.s.r. data, is illustrated in a study of R CHSR radicals and alkane-, arene-, and alkoxy-sulphonyl radicals (obtained by high-intensity u.v. irradiation of sulphinic acids in the presence of di-t-butyl peroxide at low temperatures). Further evidence for hindered rotation about the C—S bond in these species is obtained, - and an unusual order of proton hyperfine splittings a 0-H)> a (a-H) a (y-H) is reported for propanesulphonyl radicals. The potential of the e.s.r. method in conformational analysis is shown in studies of radical cations (3) from 2,5-bis(alkylthio)thiophens, where the S-cis-cis conformer (3) is identified as more stable than other rotamers this is assumed to be the case too for the neutral molecule. 

---