5- Thio-furans

There have again been a number of reports relating to the use of O2 in non-traditional environments. Thus the O2 oxidation of electron-rich substrates such as quinol, 1-naphthol and anthracene with bentonite-bound methylene blue and hydrotalcite-bound rose Bengal has been described. These clay-bound sensitizers have been recovered and reused up to three times with only a small loss in efficiency, and, it is claimed, are more stable with respect to bleaching. The fullerene-coated beads already described (Scheme 7) have been used to promote the conversion of 1-naphthol to 1,4-naphthoquinone. The conventional methylene blue sensitized oxidation of 3-bromo-2,5-bis-(thio)furans affords thiomaleates (Scheme 16) which have synthetic potential as dienophiles and Michael acceptors. The 3-bromo-2-thiofuran (105), in a similar fashion, gives a 4-oxobutanethioate whereas the 2,3-bis-(thio)furan (106) gives a y-butyrolactone. 

DimetaHation of Furan. Preparation of 2,5-bis(Methy]thio)Furan... 

Analogous compounds derived by fusion of a benzene ring to a pyrrole furan or thio phene nucleus are called indole benzofuran and benzothiophene... 

Halogens react with benzo[6]furan by an addition-elimination mechanism to give 2- and 3-substituted products (76JCS(P2)266). Treatment of benzo[6]thiophene with chlorine or bromine in acetic acid gives predominantly 3-substituted products (71JCS(B)79). 2,2,3,3,4,5,6,7-Octachloro-2,3-dihydrobenzothiophene is obtained when benzo[6]thio-phene is treated with chlorine in the presence of 1 mole of iodine (80JOC2l5l). 

Substituted TMM complexes also cycloadd to aldehydes in the presence of a tin cocatalyst such as MesSnOAc and MesSnOTs [31]. Reaction of 2-heptenal with methyl precursor (6) gave a mixture of methylenetetrahydrofurans (68) and (69). This regioselectivity is reversed with 10-undecenal and methyl precursor (5), where adduct (70) now predominates over (71). As in the carbocyclic system, the phenylthio group also functions as a regiocontrol element in reaction with cyclohexyl aldehyde. The initially formed adduct (72) eliminates the element of thio-phenol on attempted allyl rearrangement, and the overall process becomes a cycloaddition approach to furans (Scheme 2.21) [20]. 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

DIELS-ALDF.R REACTIONS Bis(methyl-thio)-1,3-ketadiene. 1,3-Bis(trimethyl-silyloxy)-l,3-butadiene. 2,5-Bis(tri-melhylsilyloxy)furanes. 5,5-Dimethoxy-1,2,3,4-tetrachlorocyclopenladiene. Di-peroxo-oxohexamethylphosphoramido-molybdenum(VI). I.thynyl p-tolyl sulfotie. I nrane. (E)-l-Metlloxy-1.3-... 

XVII XVII, 1st Supplement (combined with Volumes XVIII and XIX) XVII, 2nd Supplement 1933 1934 1952 2359-2503 2359-3031 2359-2503 One Cyclic Oxygen (S, Se or Te). Stem nuclei Furan, 27. Thiophene, 29. Hydroxy compounds Furfuryl alcohol, 112. Carbonyl compounds Butyrolactone, 234. Furfural, 272. 2-Aeetyl-thio-phene, 287. Xanthone, 355. Succinic anhydride, 404. Phthalic anhydride, 469. 

Several related methods for the preparation of differentially substituted 5-thio-2,3-trisubstituted furans were developed, which involved the formation of a thionium ion and the cyclization of this reactive intermediate into the tethered carbonyl group <02JOC1595>. 

Cyclic enol ethers and their thio analogues are formed from keto alcohols and thiols Ac(CH2)30H gives the dihydro-furan 113 on distillation cf. 114 115 116 for the preparation of 3,4-dihydropyrans and -thiopyrans 116 (Z=0 or S). 

Sulfides with a hydrogen atoms like dimethyl sulfide, dimethyl disulfide, and tetrahydrothiophene form diols under UV irradiation (795). In the tetrahydrothiophene-2HFA2 adduct the hydroxyhexafluoropropyl groups are in trans positions and the trifluoromethyl groups show nonequivalence (795). Aromatic thio compounds like thiophenols (77), diaryl sulfides (779, 180, 207), and thiophene (95) add HFA in an ortho position, as does furan (95). 

DRL100 CAS 50539-74-7 HR 3 2,2-DIMETHYL-2,3-DIHYDROBENZO-FURAN-7-YL-N-(4-BROMOPHENYL-THIO)-N-METHYLCARBAMATE... 

Bos and coworkers have developed several applications of alkyne-ketone photoadditions to organic synthesis. 2 Irradiation of a solution of acetone and 1-methylthio-l-propyne gives as a major product the cycloadduct (67) this results from selective oxetane formation due to radical stabilization by the methyl-thio group, followed by electrocyclic ring opening. Similarly, photoreaction of benzil and 1-t-butylthio-1-propyne gave the adduct (68) in 45% yield, which was transformed in 90% yield to the furan (69). 

A fundamental chemical tactic in the synthetic manipulation of heterocycies by organic chemists is the reduction of the heterocyclic ring. This chapter will review advances in the partial and complete reduction of pyrroles, furans, thiophenes and their benzo analogs, indoles, benzo[Z>]furans and benzo[Z>]thio-phenes. As appropriate, coverage will include the reduction of those benzo analogs of lesser interest isoindole, carbazole, benzo[c]furan (isobenzofuran), dibenzofuran and dibenzothiophene. 

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