Uses: it is a very important basic heterocyclic intermediate for the synthesis of benzoindocyanine dyes, and also a key intermediate for the synthesis of a variety of photochromic dyes. It is widely used in cyanine dyes, electroluminescent materials and pharmaceutical intermediates. Uses: used as dyes and pharmaceutical intermediates. It is an extremely important basic heterocyclic intermediate chemical book for the synthesis of benzoindocyanine dyes, and is also a key intermediate for the synthesis of a variety of photochromic dyes. It is widely used in cyanine dyes, electroluminescent materials and pharmaceutical intermediates. Production method: 1 β- Naphthalene hydrazine reacts with methyl isopropyl ketone to obtain 2,3,3-trimethyl-4,5-benzoindole with a yield of 82.2%. The reaction formula is: