Benzothiophene methylation

The hds of thiophen, benzothiophen, and dibenzothiophen and their methyl-substituted derivatives were compared in pulse experiments (623-723 K) over a sulphided CoO(5.6)-Mo03(11.2)/Al203 catalyst. Reactivities at 1 atm pressure were roughly the same but at hi er pressures, reactivity decreased with the number of rings. For benzothiophen, methyl substituents did not affect the reactivities, but for dibenzothiophen methyl substituents in the 4- or 4 - and 6- positions caused a decrease of desulphurization rate. Aromatic ring hydrogenation was not a prerequisite of C-S scission, which was the slow step. 

The presence of thiophene and its derivatives in crude oils was detected in 1899, but until 1953, the date at which the methyl-thiophenes were identified in kerosene from Agha Jari, Iran crude oil, it was believed that they came from the degradation of sulfides during refining operations. Finally, their presence was no longer doubted after the identification of benzothiophenes and their derivatives (Table 8.9), and lately of naphthenobenzothiophenes in heavy cuts. 

Rejnak M, Klima J, Svodoba J et al (2004) Synthesis and electrochemical reduction of methyl 3-halo-l-benzothiophene-2-carboxylates. Collect Czech Chem Commum 69 242-260... 

Another strain R. erythropolis KA2-5-1 was found to desulfurize alkyl derivatives of benzothiophene in addition to DBT and its alkyl derivatives [36], Specifically, it was able to desulfurize various methyl, ethyl, and multi-alkyl derivatives of DBT and of BT however, it could not desulfurize BT itself or 2-methyl, 5-methyl, 7-methyl, or 5,7-dimethyl derivatives of BT. The product of desulfurization of 3-methyl BT was... 

Oxidation of thiophene and its derivatives was studied using hydrogen peroxide (H2O2), t-butyl-hydroperoxide and Ti-Beta redox molecular sieve as selective oxidation catalysts. A new reaction pathway was discovered and investigated using C-13 NMR, GC, GC-MS, HPLC, ion chromatography, and XANES. The thiophene oxidized to thiophene-sesquioxide [3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b]-thiophene 1,1.8-trioxide] and the sesquioxide oxidized mostly to sulfate. 2-Methyl-thiophene and 2,5 dimethylthiophene also oxidized to sulfate and sulfone products. The Benzothiophene oxidation product was sulfone. This proposed new reaction pathway is different from prior literature, which reported the formation of thiophene 1,1-dioxide (sulfone ) as a stable oxidation product... 

Keywords thiophene, methyl-thiophene, benzothiophene, H202, Ti-Beta, mechanism, XANES. 

Die Umwandlung von Phenolen in Anilin-Derivate gelingt durch O-Substitution (in zwei Stufen) zu 2-Aryloxy-2-methyl-propansaure-amiden, deren Smiles-Umlagerung mittels Natriumhydrid in Phosphorsaure-tris-[dimethylamid] zu 2-Hydroxy-2-methyl-propansau-re-arylamiden und saure Hydrolyse dieser Amide, wie hier fur die Synthese von 4-Amino-1-benzothiophen gezeigt2 ... 

The Heck reaction was also efficient in the construction of furane and thiophene rings. These processes start form the appropriate o-halophenyl ether or sulphide. 2-Butenyl-(2 -iodophenyl)-sulfide, for example, was converted to 3-methyl-benzothiophene under standard conditions in 70% yield (3.21.).27... 

The Sonogashira reaction of 2-iodothiophene with 2-methyl-3-butyne-2-ol or trimethylsilylacetylene under phase transfer conditions using sodium hydroxide as base led to the formation of the expected products, which released their end group spontaneously under the applied conditions giving rise to the intermediate formation of 2-ethynylthiophene. This terminal acetylene, in turn, reacted with another molecule of aryl halide, yielding either non symmetrical or symmetrical diarylethynes. When 2-methyl-3-butyn-2-ol was used as acetylene equivalent68 it was possible to introduce a benzothiophene moiety in the second step, while the reaction of 2-iodothiophene and trimethylsilylacetylene led to the formation of l,2-bis(2 -thienyl)acetylene (6.47.),69... 

Reactivities of Methyl-Substituted Benzothiophenes (25) (C0M0/AI2O3, 40Cf C, 1 atm)... 

Fig. 29. Correlation between relative hydrogenolysis reactivity and the electron densities on sulfur. ( ) Reaction conditions 300°C, 71 atm, sulfided CoO-Mo03/A1203 (5). (1) DBT (2) benzo[fo]naphtho[2,3-4]thiophene (3) 7,8,9,10-tetrahydrobenzo[b]naphtho[2,3-rf]thio-phene (4) 5b,6,ll,lla-tetrahydrobenzo[fc]naphtho[2,3-d]thiophene. (O) Reaction conditions 450°C, 1 atm, sulfided CoO-Mo03/A1203(6). (5) Thiophene (6) tetrahydrothiophene (7) benzothiophene (8) 2,3-dihydrobenzothiophene. ( + ) Reaction conditions 360°C, 2.9 MPa, sulfided NiO-Mo03/Al203(3). (9) 1-Methyl-DBT (10) 2- or 3-methyl-DBT (11) 4-methyl-DBT (12) 4,6-dimethyl-DBT. (A) Reaction conditions 300°C, 102 atm, sulfided CoO-Mo03/ Al203(8). (13) 2,8-Dimethyl-DBT (14) 3,7-dimethyl-DBT (15) 4-methyl-DBT (16) 4,6-di-methyl-DBT. Reprinted with permission from Ref. 38, Ma et al. (1995). Copyright 1995 American Chemical Society.

Fig. 30. Relative hydrogenation reactivity of methyl-substituted benzothiophenes and methyl-substituted l,T-dioxodibenzothiophenes versus their C2-C3 bond order. (O) Benzothiophenes (5) BT (7) 2-methyl-BT (8) 3-methyl-BT (9) 2,3-dimethyl-BT. ( ) 1,1-Dioxoben-zothiophenes (BT02) (11) BTO2 (29) 2-methyl-BT02 (30) 3 methyl-BT02 (31) 2,8-di-methyl-BT02. Reprinted with permission from Ref. 38, Ma et al. (1995). Copyright 1995 American Chemical Society.

Furo[3,2-fa]benzothiophenes (37) were synthesized in an analogous way (91JHC269) by smooth cyclization of the cyanomethyl ether 36 in the presence of K2C03/DMF. The starting 2-cyano-3-hydroxybenzothiophene 35 was obtained from methyl 2-thiohydroxybenzoate and chloroacetonitrile. Under Vilsmeier conditions (POCl3/DMF), the 2-cyano-3-cyanomethoxy-... 

Attempted dehydrogenation of thiochroman with chloranil results in ring contraction to a mixture of 2-methyl- and 2-methyl-2,3-dihydro-benzothiophene (76KGS328). 

The chromatogram of the corresponding fraction from the Medicine River oil, Figure 12, shows the best peak resolution, and these peaks appear to represent the same benzothiophenes present in the other oils. This is believed to be a thermally mature oil, and it is therefore expected that the alkyl side chains would be reduced to methyl residues. The... 

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