Thiophene, 2,5-dihydro-3-methyl

ISOPRENE CYCLIC SULFONE (Thiophene, 2,5-dihydro-3-methyl-, 1-dioxide)... 

Dimethyl-3-oxo- Ell, 1536 (1,3-Dibrom-Verb, + NaSH)-Thiophen 3-Methyl-2,5-dihydro- -S-oxid Ell, 709 (S-Oxigenier.)... 

Thiophene, 2-amino-3-cyano-5-phenyl-synthesis, 4, 888-889 Thiophene, 3-amino-4,5-dihydro-cycloaddition reactions, 4, 848 Thiophene, 2-amino-3-ethoxycarbonyl-ring opening, 4, 73 Thiophene, 2-amino-5-methyl-synthesis, 4, 73 Thiophene, 2-anilino-synthesis, 4, 923-924 Thiophene, aryl-synthesis, 4, 836, 914-916 Thiophene, 2-(arylamino)-3-nitro-synthesis, 4, 892 Thiophene, azido-nitrenes, 4, 818-820 reactions, 4, 818-820 thermal fragmentation, 4, 819-820 Thiophene, 3-azido-4-formyl-reactions... 

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... 

D) Preparation of 4-[1 -Methyl-Piperidyl-(4 )]-9,10-Dihydro-4H-Benzol4,5]Cyciohepta[1,2-b] Thiophen-(4)-ol 0.94 g of magnesium filings which have been activated with iodine are covered with a layer of absolute tetrahydrofuran and etched with a few drops of ethylene bromide. A solution of 5.0 g of 1-methyl-4-chloropiperidine in 5 ml of tetrahydrofuran is then added dropwise and boiling then effected for a further hour under reflux. After cooling to room temperature, the solution of 4.5 g of 9,lO-dihydro-4H-benzo[4,5] cyclohepta[1,2-b] thio-phen-(4)-one in 5 ml of tetrahydrofuran is added dropwise. 

CN 4,9-dihydro-4-( 1 -methyl-4-piperidinylidene)-10//-benzo[4,5]cyclohepta[ 1,2-i]thiophen- 10-onc... 

C 9H,2N0S 34580-09-1) see Ketotifen 4,9-dihydro-4-(l-methyl-4-piperidinylidene)-10/f-benzo [4,5]cyclohepta l,2-l>)thiophen-10-one (C19H19NOS 34580-13-7) see Ketotifen... 

Thienyl sulfides with the 2-position of the thiophene ring blocked, e.g., allyl 2-methyl-3-thienyl sulfide (51), also undergo sigmatropic rearrangement when heated in quinoline [Eq. (23)]. 2,6-Dimethyl-2,3-dihydro-thieno[3,4-Z ]thiophene (52) is formed, together with other products. 

Fiessdmann and Pfeiffer" passed HCl at 0° through acetoacetic ester and thioglycolic ester in dcohol to obtain triethyl y3, -bis(carbo-methoxymethylthio)butyrate (169) Dieckmann condensation reportedly furnish ethyl 3,4-dihydroxy-6a-methyl-3a,6a-dihydro-thieno(2,3-b]-thiophene-2-carbOxylate (170) [Eq. (48)]. 

Formylbenzeneboronic acid reacts with hydroxylamine to give a cyclized oxime (200), and the thiophene analogue (201) was prepared in a similar way. These fused 3//-1,2,3-azoxaborines are analogs of the above-mentioned 2,3-dihydro-l,2,3-diazaborines. Compound (200) is resistant to hydrolysis and air, but cannot be converted to its 5-methyl derivative. 

The mass spectra of 2-phenyl-, 3-phenyl-, and 3-methyl-2-phenyl-benzo[6]thiophene have been discussed, and tentative structural assignments of the main fragment ions have been made.121 The mass spectra of benzo[6]thiophene-l, 1-dioxide and its 2,3-dihydro derivative have been examined in detail.121> 127 The partial mass spectrum of 2,3-dihydrobenzo[6]thiophene has been recorded.124... 

Reduction by LiAlH4 of 2,3-dihydrothieno[3,2-6]thiophen-3-one (22) and its 2-methyl- and 2-ethyl-derivatives afforded the appropriate thienothiophene 2.21,25,28,29 Similarly, Gronowitz and co-workers48 used borohydride reduction of ketones 33 and 34 to prepare 2-methyl-thieno[3,2-6]thiophene (35). Attempts to reduce 2,3-dihydrothieno[3,2-6]thiophen-3-one (22)28 and 2,3-dihydro-4,6-dimethylthieno[3,4-6]-thiophen-3-one (87)T with zinc powder in acetic acid were unsuccessful. 

Alternative synthetic techniques towards TB derivatives were reported by Becker (93TL1889) and Cekavicus (01TL4239). Becker prepared a highly functionalized TB derivative by heating methyl 5-chloro-4-[(ethoxyoxoacetyl)amino]-2-methoxybenzo-ate in DMSO at 180°C. Cekavicus reported that the novel heterocyclic system 3 arose via the intermolecular Mannich reaction of l,l-dioxo-l,2-dihydro-ben-zo[i]thiophen-3-one (Scheme 4). 

E) Preparation of 4-[l -Methyl-Piperidylidene-(4 )]-9,10-Dihydro-4H-Benzo[4,5]Cyclohepta[l,2-b]Thiophene Hydrochloride 2 g of 4-[l -methyl-piperidyl-(4 )]-9,10-dihydro4H-benzo[4,5]cyclohepta[l,2-b]thiophen-(4)-ol, 60 ml of glacial acetic acid and 20 ml of concentrated hydrochloric acid are boiled for 30 minutes under reflux. After evaporating in a vacuum, the residue is triturated with 3 ml of acetone, the precipitated hydrochloride is then filtered off and it is recrystallized from isopropanol/ether. MP 261° to 263°C (decomposition). 

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. 

Benzo(6]thiophene halogenation, 57, 294 iodination, 59, 254 resonance energy, 56, 352 Ru, Ir complexes, 58, 150 Benzo[6]thiophene, 3-benzoyl-, reaction with hydrazine, 56, 128 Benzo[l)]thiophene, 3-bromo-, chlorination, 57, 293 Benzo[6]thiophene, 4-fluoro-, 60, 17 Benzo[/>)thiophene, 4,5,6,7-tetrafluoro-2,3-dihydro-2-methyl-, 60, 28 Benzo(e]thiophenes, resonance energy,... 

---