The phenanthridinone heterocyclic system has attracted considerable attention in recent years due to the diverse array of physical, chemical and pharmacological properties demonstrated by natural and synthetic derivatives. As a consequence there has been considerable development of synthetic methodology for the synthesis of this and related heterocyclic ring systems. The synthetic literature is discussed and is compared with a direct arylation methodology for the intramolecular cyclization of tertiary (2-iodo)benzoylamides to generate the biaryl bond of these compounds. The efficient methodology allowed the synthesis of a number of previously unknown phenanthridinone products. The photoluminescent properties of representative examples were characterized and it is proposed that the previously unknown compound 1s reveals dual fluorescence in a manner similar to the known compound 1r.

Rate constants for the quenching of 1,3-indandione (1) triplet by olefins and by hydrogen and electron donors were obtained employing the laser flash photolysis technique in benzene solution. These rate constants ranged from 2.5x10(5) Lmol-1s-1 (for 2-propanol) to 5.9x10(9) Lmol-1s-1 (for DABCO). From the quenching rate constants by 1,3-cyclohexadiene, trans- and cis-stilbene a value between 49.3 and 52.4 kcal/mol was estimated for the energy of the triplet state of 1,3-indandione. The npi* character of this triplet state was evidenced by the quenching rate constants obtained when typical hydrogen donors were employed as quenchers. For 2-phenyl-1,3-indandione (2, R=phenyl) a fast Norrish type I reaction is operating which prevents the determination of kinetic and spectroscopic data of its triplet state.

A técnica de fotólise por pulso de laser de nanossegundo foi empregada no estudo da reatividade do triplete de 1,2-aceantrilenodiona (1) frente a fenóis. As constantes de velocidade de supressão (k q), em acetonitrila, variaram de 3,3 x 10(5) L mol-1 s-1 (fenol) a 1,3 x 10(7) L mol-1s-1 (4hidroxifenol), com os fenóis contendo substituintes doadores de elétrons mostrando-se mais reativos. O efeito isotópico cinético (kH/kD) observado para a supressão de 1 por 4-metoxifenol foi de 1,5. O gráfico de Hammett para a reação do triplete de 1 com fenóis forneceu uma constante de reação ro = 1,04, em acetonitrila. O baixo valor encontrado para a constante de velocidade de supressão deste triplete com 1,3-cicloexadieno (k q=2,0 x 10(4) L mol-1s-1), assim como o fato de que a constante de velocidade de supressão por beta-caroteno é controlada por difusão, sugerem que a energia do triplete de energia mais baixa para 1,2-aceantrilenodiona situa-se entre 88 e 219 kJ mol-1.

The nanosecond laser flash photolysis technique has been used to study the reactivity of 1,2-aceanthrylenedione (1) triplet towards phenols. Using acetonitrile as solvent, the quenching rate constant k q ranged from 3.3 x 10(5) L mol-1s-1 (phenol) to 1.3 x 10(7) L mol-1s-1 (4hydroxyphenol). Phenols with electron donating substituents were more reactive. The kinetic isotope effect (kH/kD) observed for the quenching of 1 with 4-methoxyphenol was 1.5. The Hammett plot for the reaction of the triplet of 1 with phenols gave a reaction constant rho = 1.04 in acetonitrile solution. The low value for the quenching rate constant measured for this triplet with 1,3-cyclohexadiene (k q=2.0 x 10(4) L mol-1s-1) and the diffusion controlled quenching rate constant obtained for beta-carotene suggest that the energy of the lowest triplet state for 1,2-aceanthrylenedione is located between 88 and 219 kJ mol-1.