Borane → 2-(o-Hydroxyphenylthio)-4-nitrobenzyl alcohol

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Reaction Steps

9-Cyano-6H-dibenz[b,e][1,4]oxathiepin (IIa) may be prepared according to the following general reaction scheme: ##STR6## wherein R2 and R3 are as previously defined, by treating an appropriately substituted (R2 and/or R3) o-aminothiophenol with 2-chloro-4-nitrobenzoic acid in the presence of cuprous oxide to form the corresponding 2-(o-aminophenylthio)-4-nitrobenzoic acid which then is suspended in water, acidified with sulfuric acid, treated with sodium nitrite followed by sodium fluoroborate to obtain the diazonium fluoroborate which is heated in 50% sulfuric acid to obtain the corresponding 2-(o-hydroxyphenylthio)-4-nitrobenzoic acid. The acid product is treated with borane in tetrahydrofuran to form the corresponding 2-(o-hydroxyphenylthio)-4-nitrobenzyl alcohol which is cyclized in the presence of dicyclohexylcarbodiimide (DCC) to form the corresponding 9-nitro-6H-dibenz[b,e][1,4]oxathiepin. The nitro group then is reduced to the 9-amino compound with stannous chloride and the amine is treated with sodium nitrite followed by a mixture of cuprous cyanide and potassium cyanide to obtain the desired 9-cyano-6H-dibenz[b,e][1,4]oxathiepin of formula IIa.

Provenance & Evidence