Benzo thiophenium salts

Benzo[b]thiophenium, 1,2,3,5-tetramethyl-theoretical methods, 4, 3 Benzo[b]thiophenium salts preparation, 4, 723-724 Ben2o[b]thiophen-4-one, 4,5,6,7-tetrahydro-synthesis, 4, 905-906 5H-Benzo[b]thiophen-4-one, 6,7-dihydro-synthesis, 4, 900 Benzo[b]thiophyne, 4, 750 1H- 1,3,4-Benzotriazepine, 2,3-dihydro-synthesis, 7, 637 1H-1,2,4-Benzotriazepines synthesis, 7, 638 1,2,5-Benzotriazepines synthesis, 7, 640... 

On converting l-phenylbenzo[ ]thiophene into 1-phenyl-1-benzo[ ]thiophenium triflate 123, this salt becomes a dienophile and reacts readily with cyclopentadiene or l,3-diphenylbenzo[r]furan to give the adduct 124 (Scheme 9) <19990L257>. This example of the dienophilic nature of the double bond in the benzo[/ ]thiophene ring arises from reduced aromaticity. Thiophene 1-oxide and 1-substituted thiophenium salts present reduced aromaticity <1970JA7610>. 

Studies in solution suggest specific association of chloroform with the benzo [b] thiophene molecule and interaction of acetone with the sulfur atom.67 Complexation constants of benzo [b]thiophene with polar solvents (e.g., DMF, 2-pyrrolidone) have been determined by an NMR method.77 In the complex of benzo [b] thiophene with Ag+, the metal ion is strongly associated with the lone pair of electrons on the sulfur atom78 in the 1,3,5-trinitrobenzene complex, NMR data suggest that the trinitro compound lies over the phenyl ring of the heterocycle.78,79 Likewise, in the chromium tricarbonyl complex, the Cr(CO)3 group is bonded to the benzenoid ring.80 Studies of the structure of benzo[b]thiophenium salts will be discussed in Section III,A,2. 

Amongst the derivatives of thiophene, the chemistry of thiophenium salts and S,C- and S,N-thiophenium ylids has also been reviewed <89AHC(45)151> as has the chemistry of the thiophene 1-oxides, 1,1-dioxides, and sesquioxides <85HC(44/l)572>. The chemistry of benzo[Z>]thiophenes has been reviewed by Scrowston <8iAHC(29)l7l> and there is a study by Gronowitz on the isomeric dithienothiophenes <94JHC64l>. 

The alkylation of thiophene and benzo[6]thiophene to form 1-alkylthiophenium and 1-alkyl-benzo[i]thiophenium salts was discussed in CHEC-1 <84CHEC-l(4)765>. l-Methylbenzo[6]-thiophenium fluoborate has been obtained also by methyl transfer from 0-methyldibenzofuranium... 

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