Annulation with thiophene synthesis of benzothiophenes

Alkylation of 1 with phenacyl bromide derivatives in the presence of sodium ethoxide gave tricarbonyl 145, which were cyclized to ben-zo[fr]thiophenes 146 upon treatment with La wesson s reagent (99JHC687). Tetrahydrobenzothiophenes 146 with hydroxylamine hydrochloride afforded syn/antioximes 147, which upon treatment with PPA underwent a regiospecific ring expansion to thieno[3,2-c]azepinones 148 (99JHC687). 

The analogue 149 was prepared from 1 with ethyl cyanoacetate and sulfur. Its reaction with ethyl oxalyl chloride gave 150 whose hydrolysis 

Alkylation of the sodium salt of 152 with allyl bromide in DMSO afforded the 3-S-allyl 160 (R = H), which underwent a thio-Claisen rearrangement in the presence of p-toluenesulfonic acid to give 2-allyl-3-mercapto 161 (R = H) that cyclized partially during purification to hexahydrothiophene 162 (R = H). Alternatively, acetylation of 161 (R = H) gave 163, which cyclized on heating in quinoline to afford 162 (R = H). Similarly, 2-butenyl 160 (R = Me) gave 161 (R = Me) but the 

Condensation of 1 with carbon disulfide in the presence of potassium carbonate in DMF afforded dithioketene anion 164 that upon reaction with ethyl bromoacetate and methyl iodide in DMF led to the formation of 4,5,6,7-tetrahydrobenzo[c]thiophene 165 (95SC2449). Derivative 166 was reported in a patent (06WOP98). 

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