2.5- Dihydro-3-methylthiophene

Complexes 79 show several types of chemical reactions (87CCR229). Nucleophilic addition may proceed at the C2 and S atoms. In excess potassium cyanide, 79 (R = R = R" = R = H) forms mainly the allyl sulfide complex 82 (R = H, Nu = CN) (84JA2901). The reaction of sodium methylate, phenyl-, and 2-thienyllithium with 79 (R = R = r" = R = H) follows the same route. The fragment consisting of three coplanar carbon atoms is described as the allyl system over which the Tr-electron density is delocalized. The sulfur atom may participate in delocalization to some extent. Complex 82 (R = H, Nu = CN) may be proto-nated by hydrochloric acid to yield the product where the 2-cyanothiophene has been converted into 2,3-dihydro-2-cyanothiophene. The initial thiophene complex 79 (R = R = r" = R = H) reacts reversibly with tri-n-butylphosphine followed by the formation of 82 [R = H, Nu = P(n-Bu)3]. Less basic phosphines, such as methyldiphenylphosphine, add with much greater difficulty. The reaction of 79 (r2 = r3 = r4 = r5 = h) with the hydride anion [BH4, HFe(CO)4, HW(CO)J] followed by the formation of 82 (R = Nu, H) has also been studied in detail. When the hydride anion originates from HFe(CO)4, the process is complicated by the formation of side products 83 and 84. The 2-methylthiophene complex 79... 

C3H402S, 2H-Thiete 1,1-dioxide C4H602S, 2,5-Dihydrothiophene 1,1-dioxide C4H602S, 2,3-Dihydrothiophene 1,1-dioxide CsHgOjS, 2,5-Dihydro-2-methylthiophene 1,1-dioxide C5H802S, 2,5-Dihydro-3-methylthiophene 1,1-dioxide... 

The reduction of 2-methylthiophene, however, yielded only small amounts of dihydro-2-methylthiophene and a high yield of pcntcnethiol. It was apparent that substitution in the 2-position inhibited the production of the dihydrothiophene and favored more complete reduction. It was interesting to note that the reduction of 2,5-dimethylthiophene furnished small amounts of hexan-2-one. It was believed that the crude hexenethiol probably contained some hexene-2-thiol-2 which is capable of isomerization to hexane 2-thione from which the ketone can be formed by the action of alkali as follows ... 

Figure 8 outlines possible routes leading to cysteine specific products via 1-deoxypentosone. Under the chosen reaction conditions, (180 °C H-O) norfuraneol is further transformed via 4-hydroxy-5-metnyl-3-(2H)-thiophenone and 2-methyl-3-(2H)-thiophenone, into 2-methyl-3-mercapto-thiophene and 2-methylthiophene, respectively. Norfuraneol is a methylene active compound, which undergoes aldolcondensation with carbonyls forming colored nonvolatile products. 2-Mercaptopropionic acid may be formed from the mercaptoketone by oxidative cleavage. By this route 2-methyl-3-thiolanone and 2-methyl-4,5-dihydro-thiophene may result. 

C5H5BrS 3-bromo-4-methylthiophene 30318-99-1 454.15 39.497 1,2 4549 C5H602 dihydro-3-methylene-2 3H)-furanone 547-65-9 412.82 35.575 2... 

J.25) 3(2/f)-Thiophenone, dihydro-2-methyl-, tetrahydro-2-methylthiophen-3-one, 2-methylthiolan-3-one, 2-methylthiophan-3-one [13679-85-1] FEMA 3512... 

The thermal equilibrium between 2,3-dihydro-2,3-dimethylenethiophene (29) and 1,2-dihydro-cyclobuta[ ]thiophene (30) has been investigated (Equation (2)) <88CB79l >. The former was prepared by 1,4-elimination of HCl from 2-(chloromethyl)-3-methylthiophene in the vapor phase at 600°C. The results of photoelectron spectroscopic analysis in the gas phase as well as UV/vis-absorption spectroscopy in an argon matrix indicate no evidence for the ring-closed form (30). However, interconversion of (29) and (30) was achieved by irradiation in an argon matrix with light of the appropriate wavelength. 

Representative procedure for the gold-catalyzed cycloisomerization of a-thioallenes. Trans-2,5-dihydro-5-isopropyl-2-(methoxymethyl)-3-methylthiophene ... 

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