7470-93-1

Photolyses of 1-alkoxy-9-diazoanthrones 12 in benzene induce abstraction of hydrogen from the side chain, followed by cyclization (→ 15 → 16) or disproportionation (→ 17 + 18) of the intervening biradicals 20. In alcohols, reduction of triplet anthronylidenes (314 → 21 → 22) competes with the formation of 20, and intramolecular electron transfer of 20 leads eventually to the acetals 24.

The regioselectivity of reduction of 1-substituted anthraquinones to 1 - or 4-substituted anthrones is determined by both the nature of the substituent and the type of the reducing system used.

Several substituted anthracenes, benzanthracenes, dibenzanthracene, and more complex ring system derivatives are formed by the cycloaddition of 1,3-bis(trimethylsilyl)isobenzofuran (2) with arynes generated by LTMP-induced dehydrohalogenation of readily accessible haloaromatics.The cycloadducts undergo a novel acid-induced conversion to anthracenones.For several substrates this reaction is highly regioselective, allowing position specific introduction of another substituent at this stage.Reduction/dehydration of the anthrones provides an expeditious route to various polycyclic aromatic hydrocarbons.

Stereodynamics of a variety of 9-(3,5-dimethylbenzyl)triptycene derivatives was studied.Atropisomerism about the bridgehead-to-methylene bond was realized in a triply peri-substituted derivative, 8,13-dichloro-1,4-dimethyl-9-(3,5-dimethylbenzyl)triptycene: the activation enthalpy for the ap--> +/-sc conversion was 26.4 kcal/mol.Barriers to rotation about the bridgehead-to-methylene bond in a variety of triply, doubly, and singly peri-substituted derivatives were obtained by DNMR method.DNMR behavior of the diastereotopic m-methyl groups in the benzyl moiety revealed the dual mechanisms of the methyl exchange process; rotation about the methylene-to-aryl bond by 180 deg without rotation about the bridgehead-to-methylene bond ("isolated rotation (IR)") and rotation about the methylene-to-aryl bond by 180 deg synchronous with rotation about the bridgehead-to-methylene bond by 120 deg ("gear motion (GM)").The GM process predominates in peri-unsubstituted derivatives, while the IR process predominates in triply peri-substituted ones.