PREPARATION OF (BENZO)ISOQUINOLINES USING in situ GENERATED ARYNE INTERMEDIATES

(Benzo)isoquinoline derivatives are of significant interest in different areas of basic and applied organic chemistry. Of special promise are their biological [1-3], photophysical, and coordination [4-8] properties. Their use as chiral catalysts [9, 10] is also of interest. The most frequently used methods for preparing (benzo)isoquinoline systems are cross-coupling reactions [11, 12], which demand the use of special catalysts. We propose a method for preparing (benzo)isoquinoline derivatives based on an aza Diels–Alder reaction with 1,2,4-triazines as dienes and the aryne intermediates acting as dienophiles. The methodology for preparing diverse pyridine derivatives via reaction of the corresponding 1,2,4-triazines has long been known [13-15]. However, there are only a few examples of using aryne intermediates in similar reactions. The range of dienophiles in these cases is limited to certain dehydrobenzene derivatives, the generation of which used poorly available anthranilic acids [16, 17] despite the marked growth in the chemistry of arynes in recent years [18, 19]. In our work, we propose a highly efficient method for the preparation of (het)aryl-substituted isoquinoline 1a and benzo[h]isoquinoline 1b, which involves the reaction of arynes 2a,b with the substituted 1,2,4-triazines 3a,b in anhydrous toluene for 24-36 h at 140°C under an argon atmosphere. The targe