Hydrazide

Hydrazides in organic chemistry are a class of organic compounds with the formula R−NR1−NR2R3 where R is acyl (R'−C(=O)−), sulfonyl (R'−S(=O)2−), phosphoryl ((R'−)2P(=O)−), phosphonyl ((R'−O−)2P(=O)−) and similar groups (chalcogen analogs are included, for example sulfur analogs called thiohydrazides),[1] R1, R2, R3 and R' are any groups (typically hydrogen or organyl).

[2] Unlike hydrazine and alkylhydrazines, hydrazides are nonbasic owing to the inductive influence of the acyl, sulfonyl, or phosphoryl substituent.

When derived from ketones, these hydrazones participate in the Shapiro reaction[3] and the Eschenmoser–Tanabe fragmentation.

[9] After 4 hours at 110 °C, the indole ring structure has been broken into (2-amino-5-fluoro-phenyl)-acetic acid hydrazide with reduction of the ketone at the 3-position.

Subsequent annelation in strong acid creates the 1,3-dihydro-2-oxo indole structure required for the drug.