Thiophenes methoxy

Methylthiophene is metallated in the 5-position whereas 3-methoxy-, 3-methylthio-, 3-carboxy- and 3-bromo-thiophenes are metallated in the 2-position (80TL5051). Lithiation of tricarbonyl(i7 -N-protected indole)chromium complexes occurs initially at C-2. If this position is trimethylsilylated, subsequent lithiation is at C-7 with minor amounts at C-4 (81CC1260). Tricarbonyl(Tj -l-triisopropylsilylindole)chromium(0) is selectively lithiated at C-4 by n-butyllithium-TMEDA. This offers an attractive intermediate for the preparation of 4-substituted indoles by reaction with electrophiles and deprotection by irradiation (82CC467). 

Benzo[b]thiophene, 3-mercapto-2-methyl-synthesis, 4, 931 Benzo[6]thiophene, 2-methoxy-lithiation, 4, 773 synthesis, 4, 929 Benzo[6]thiophene, 3-methoxy-alkylation, 4, 765 synthesis, 4, 929 Benzo[6]thiophene, 4-methoxy-anodic oxidation, 4, 798 Benzo[6]thiophene, 5-methoxy-synthesis, 4, 929 Benzo[6]thiophene, 6-methoxy-synthesis, 4, 929 Benzo[6]thiophene, 7-methoxy-synthesis, 4, 929-930... 

Benzo[6]thiophene-3-acetic acid, 5-methoxy-synthesis, 4, 879... 

Of greater importance is the reaction of unsaturated compounds with sulfur at 200-250°C, which normally leads to l,2-dithiole-3-thiones (trithiones) but especially with 2-aryIsubstituted 2-butenes and 1- aryl- or 2-aryl-1-butenes, thiophenes are obtained in 15-60% Thus p-methoxy-a-ethylstilbene (50) gives 2-phenyl-3-... 

The a-selectivity is illustrated by the fact that 2-alkyl-, > 2-methoxy-, > and 2-alkyIthio-thiophenes and alkyl thenyl sul-fides ° are metalated exclusively in the 5-position. In electrophilic aromatic substitution, as previously mentioned, an appreciable amount of 3-substitution is obtained with some of these groups. After acetalization ketones can also be metalated. Thus from the diethyl ketal of 2-acetylthiophene, 2-acetyl-5-thiophenealdehyde was obtained after metalation with n-butyllithium followed by the reaction of the metalorganic compound with A,A -dimethylformamide. ... 

Methoxy-4H-ben2o[4.5] cyclohepta[1.2-b] thiophen-4-one Hydrogen chloride... 

The chloroform solution is concentrated and the residue recry stall i2ed from 270 cc of absolute ethanol. The pure 10-methoxy-4-(1 -methyl-4-piperldyl)-4H-ben2o[4,5] cyclohepta[1,2-b] -thiophen-4-ol base, having a melting point of 194°C to 196°C, is obtained in this manner. Microanalysis corresponds with the formula Q20H23NO2S. 

Amixture of 3.4 gof 10-methoxy-4-(1 -methyl-4-piperidyl)-4H-ben2o[4,5]cyclohepta[1,2-b]-thiophen-4-ol base and 40 cc of 3 N hydrochloric acid is kept in a boiling water bath at 95°C to 100°C for 1 hour. The mixture is subsequently made alkaline with concentrated caustic soda solution at 20°C while cooling, and the free base Is extracted with chloroform. The chloroform solution is concentrated, and the residue is recrystalli2ed from ethanol/water 1 1. The pure 4-(1 -methyl-4-piperldylidene)-4H-ben2o[4,5]cyclohepta[1,2-b] thiophen-10(9H)-one base, having a melting point of 152°C to 153°C, is obtained in this manner. 

As we found that furan and thiophene substituted oximes can be used as substrates for the INOC reactions (Eq. 5) [29b] similarly, furan substituted nitro alkane 134 is also a good substrate for INOC reactions (Eq. 13) [40]. The furfuryl derivative 134, prepared via Michael addition of furfuryl alcohol to 4-methoxy- -nitrostyrene, was subsequently transformed without isolation of the intermediate nitrile oxide 135 to the triheterocyclic isoxazoline 136 as a 5 1 mixture of isomers in high yield. 

Also as noted above any substituents present have little effect upon such oxidations. In 2,2 -methylenedifuran (118) the rings are attacked simultaneously giving a tetramethoxy derivative.297 Even the bulk of the fert-butyl group has little effect.298 The only marked substituent effect is that exerted by an aromatic (benzene, thiophene, furan) residue which, if directly attached at the 2-position, promotes elimination instead of the addition of another methoxy group. The net process then becomes one of arylation, as when 2-(2-thienyl)furan (119) is oxidized to 120.298 There are reports that acetyl and carboxy groups can be ejected during oxidation, but that ester groups are usually retained.287... 

Studies by Heinze etal. on donor-substituted thiophenes or pyrroles [33] such as methylthio (= methylsulfonyl) or methoxy-substituted derivatives provide further clear evidence for this reaction pathway. They found, for instance, that 3-methylthiothiophene or 3-methoxythio-phene (2) undergo a fast coupling reaction. However, deposition processes or insoluble film formation could not be detected in usual experiments with these compounds, even at high concentrations. Similarly, the corresponding 3,3 -disubstituted bithiophenes (2a) do not polymerize, but the anodic oxidation of 4,4 -disubstituted bithiophenes (2c) produces excellent yields of conducting polymers. 

A careful analysis based on these experimental results excluded a chain-propagation process [33a]. On account of the 3-position of the methylthio or methoxy substituent in the thiophene or pyrrole rings, three isomeric dimers may be formed. The main reaction path can be deduced from the mesomeric forms of the radical cations (2)". The two most important mesomeric structures are those with the unpaired electron in... 

With the exception of 4-methoxydibenzothiophene, which is well characterized, the literature concerning the remaining three mono-methoxy compounds is somewhat confused. As mentioned earlier (Section III, C, 3), dibenzothiophene is metabolized as 1 -hydroxydibenzo-thiophene 5,5-dioxide, which was converted to the corresponding methoxy compound by methylation for structure determination. The position of the methoxy group was determined by the fact that the melting point of the product was different from those of the other three methoxy sulfones, each of which was listed for the first time, but without details of source or preparation. Tilak had attempted the preparation of... 

First examples of stable carbocations were reported from several classes of thia-PAHs with four fused rings, namely, benzo[Z ]naphtho[2,l-J thiophene (40) and its 3-methoxy derivative (41), phenanthro[4,3-Z ]thiophene (42) and its 7-methoxy (43), 10-methoxy (44), and 9-methoxy (45) derivatives, phenanthro[3,4-Z ]thiophene (46) and its 7-methoxy (47) and 9-methoxy (48) derivatives, and 3-methoxybenzo[Z ]-naphtha[l,2-J thiophene (50) (Fig. 25). Regioselectivity issues and charge... 

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