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Benzothiophenes rearrangement

A number of reactions have been investigated which could form a thiophene ring by forming a bond y to the sulfur atom, but which have not been generalized. Photocyclization of phenylthioethylenes has led to benzothiophenes, usually in low yields, and sometimes accompanied by rearrangement (68JOC2218). Irradiation of (115 R = H or Me, and R1 = Ph) in the presence of iodine gave a mixture of (116) and (117) in about 11% maximum yield. If R1 = H or Me, no product (117) was found, and if R was Ph, only traces of cyclized products were detected. A complex mechanism was proposed to account for these results. [Pg.880]

Another useful source of the CS fragment in this synthesis scheme is dichlorosulfine. It has been shown to react with diaryldiazomethanes to yield 2-chlorobenzo[h]thiophene 1-oxides in reasonable yields (72RTC1345). The reaction is quite successful when X = H, 4-Me, 4-C1 or 3-OMe (Scheme 20) but failed when X = 4-OMe. The reaction presumably proceeds by a [3 + 2] cyclization to form an intermediate thiadiazole derivative, which loses nitrogen to give an episulfoxide that can rearrange to the final product (Scheme 20). Since benzothiophene sulfoxides are easily reduced, this constitutes a new thiophene synthesis. [Pg.894]

Addition of dimethyl acetylenedicarboxylate (DMAD) to the benzothiophene 59 (Equation 2) followed by rearrangement results in an interesting formal [2+2] cycloaddition leading to product 60 <2006BML3034>. [Pg.941]

Photochemical 27t-27t cycloaddition of benzo[l,2- 4,5-6 Jdithiophene and substituted acetylenes have been used to synthesize cyclobuta[6]thieno[2,3 /][I]benzothiophenes 103 <03JOC8258>. Both disubstituted acetylenes and diynes have been shown to undergo this type of 27t-27i photoaddition and moreover the addition was found to undergo via a syn addition. Photoirradiation of tris(2-benzo[6]thienylmethane) 104 in acetonitrile undergoes a di-7t-methane rearrangement to produce a cyclopropane, which upon further irradiation is easily converted to a secondary product, a thiopyran 105 <03TL751>. [Pg.112]

Phenyl vinyl sulfides cyclize to substituted benzothiophenes on photolysis. They also rearrange during photolysis to give rearranged benzothiophenes (46). The rearrangement reaction and the elimination of hydrogen (presumably to give the benzothiophene molecule ion) are both prominent processes in the mass spectra of the aryl vinyl sulfides.88)... [Pg.125]

Benzothiophene-4-ol 76 was transformed into 4-amino-benzothiophene 79 via 2-methylpropionamide derivative 77 (Scheme 30). The rearrangement was carried out imder harsh conditions using sodium hydride in HMPA [29] or in DMF-DMPU [52], at 100 °C. [Pg.180]

The related benzene 361 and benzothiophene 363 derivatives (Scheme 120) also rearranged [ 154] but the yields of the respective products were markedly lower. [Pg.237]

The employment of aryl 2-chloroprop-2-enyl sulfides (or ethers) as thio-Claisen rearrangement substrates neatly eliminates the necessity for an oxidative step, thus providing a route to 2-methyl-benzothiophenes (-benzofurans). " ... [Pg.439]

From the 5-silyl derivatives of o-alkynylarylthiols, cycloisomerization leads to 3-silyl-benzothiophenes. The gold salt is found to be highly effective in promoting Meyer-Schuster rearrangement. ... [Pg.211]


See other pages where Benzothiophenes rearrangement is mentioned: [Pg.109]    [Pg.142]    [Pg.150]    [Pg.65]    [Pg.426]    [Pg.209]    [Pg.126]    [Pg.101]    [Pg.203]    [Pg.142]    [Pg.150]    [Pg.75]    [Pg.109]    [Pg.865]    [Pg.872]    [Pg.901]    [Pg.142]    [Pg.150]    [Pg.322]    [Pg.109]    [Pg.865]    [Pg.872]    [Pg.901]    [Pg.860]    [Pg.189]    [Pg.6583]    [Pg.145]    [Pg.31]    [Pg.3399]    [Pg.229]    [Pg.229]    [Pg.142]    [Pg.150]    [Pg.122]    [Pg.189]    [Pg.218]   
See also in sourсe #XX -- [ Pg.487 ]

See also in sourсe #XX -- [ Pg.487 ]

See also in sourсe #XX -- [ Pg.487 ]




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