1H-ISOCHROMENE-1-ONES AND ISOQUINOLINE-1(2H)-ONES
 WITH CARBONYL GROUP IN POSITION 3:
 FEATURES OF SYNTHETIC APPROACHES AND TRANSFORMATION

Oxygen-containing heterocyclic 1H-isochromen-1-ones are core structural components of various natural products and biologically active compounds. They are used as functional substrates in the synthesis of biologically active 1H-isochromen-1-ones and isoquinolin-1(2H)-ones exhibiting different biological properties and diverse applications. Synthetic approaches to these classes of heterocyclic compounds developed in parallel from the very beginning because one of the strategies for the synthesis of isoquinolin-1-one is the recyclization of the isochromen-1-one system by the action of primary amines. In this review, we comprehensively describe the synthesis of 1H-isochromen-1-ones and isoquinolin-1(2H)-ones with a carbonyl function in position 3, summarize their use as synthons in organic chemistry and highlight their biological activities.