Sho Nakazawa

Heterocycles by cycloaddition. Part II. Cycloaddition–extrusion reactions of five-membered mesoionic compounds with benzyne: prepartion of benz[c]azole and benzo[c]thiophen derivatives

Several five-membered mesoionic compounds react with benzyne to give benzo-fused five-membered heterocycles [(2) and (5)] with a formal quinonoid structure. A bridged intermediate adduct (4c) was isolated from the reaction of benzyne with a mesoionic thiazol-4-one (3c). Pyrolysis of the adduct gave an isobenzothiophen (5a), whereas its photolysis led to an isoquinolone (7). The corresponding adduct S-oxide (4e) gave the isoquinolone (7) by both pyrolysis and photolysis.

Reactions of spiro-indazoles containing keto-groups. Syntheses of benz[a]aceanthrylenes, naphth[2,1-a]aceanthrylenes, and fluoranthenes

Anthrone-10-spiro-3′-3′H-indazole (1) and 3H-indazole-3-spiro-1′-naphthalen-4′(1′H)-one (3), prepared by the cycloaddition of benzyne with 10-diazoanthrone (6) and 4-diazonaphthalen-1(4H)-one (7), respectively, thermally rearranged with elimination of nitrogen to 8-hydroxybenz[a]aceanthrylene (9b) and 3-hydroxyfluoranthene (11b), respectively. The diazoketone (6) reacted with 1,2-naphthyne to give anthrone-10-spiro-3′3′H-benz[g]indazole (4) and anthrone-10-spiro-1′-1′H-benz[e]indazole (5), which gave the rearrangement product, 10-hydroxynaphth [2,1-a]aceanthrylene (12b) by thermolysis. Photolysis of the spiro-indazoles afforded the rearrangement and/or photo-oxidation products. Thermolysis and photolysis are accountable on the basis of formation of biradicals [(14), (18), (19), and (21)] and isomerization of these to fused polycyclic compounds. In particular, the isomerization of the biradical (21) to (12b) involves the formation of the naphtho[a]cyclopropene (20).

Syntheses and reactions of spirocyclopropaneanthrones. Part 1. Reactions of p-diazo-ketones with p-quinone methides

The carbenic reaction of 10-diazoanthrone (1) with 10-methyleneanthrone (2) gave dispiro[anthrone-10, 1′-cyclopropane-2′, 10″-anthrone](3), which thermally rearranged with synchronous ring expansion, yielding spiro[2H-aceanthrone-2, 10′-anthrone](7). Similar reactions of diazonaphthalen-1 (4H)-one (11) with the quinone methide (2) and of the diazo-ketone (1) with 2, 6′-di-t-butyl-4-methylenecyclohexa-2, 5-dien-1-one (16) afforded directly the rearrangement product, 10-hydroxytribenz[a, de, j]anthracen-5-one (12), and the cyclopropyl ring-opening product, 10-(4-hydroxy-3, 5-di-t-butylbenzyl)anthrone (17), respectively, instead of the dispiro-compounds.

Selectivity in the thermal and photochemical fragmentation of the cycloadduct from benzyne and a mesoionic thiazol-4-one

During the preparation of benzo-condensed five-membered heterocycles by cycloaddition–extrusion reaction of benzyne with mesoionic compounds, a cycloadduct with a thiazol-4-one was isolated, which behaved differently on pyrolysis and photolysis.