As 1,4-benzoquinonas são encontradas em toda a natureza, podendo ser sintetizadas por diversas estratégias. Esta revisão apresenta os desenvolvimentos recentes das metodologias de síntese, das reações de ciclo adição, da química computacional e dos estudos de pulso radiolítico. Destaca ainda a sua significância química e biológica e de seus compostos derivados.1,4-Benzoquinones are ubiquitous in nature and can be synthesized by diverse strategies. Recent developments on their synthetic methodologies, cycloaddition reactions, computational chemistry and pulse radiolytic studies are reported in this review. Their chemical and biological significance as well as their derivates' are also covered.

DFT-B3LYP and CASSCF calculations have been performed using a 6-31G* basis set to study photocycloaddition reactions of biradicals, generated by irradiation of 6-amino-2-(3-thienoyl)-1,4-benzoquinone, with ethylene. The calculated parameters of biradicals and transition states have also been compared with ground state parameters to completely elucidate the reaction mechanism of [2 + 2] and [3 + 2] photocycloaddition reactions. Preference for a particular cycloaddition pathway is ascertained by the relative stability between initially formed triplet biradical and another triplet biradical formed by hydrogen shift.

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A convenient three step synthesis of 2-(2'-thiophenoacetyl)-l,4-benzoquinone and derivatives via readily available starting materials is described. The synthesized quinones have been characterized by spectral data.

Synthesis and Semiempirical Studies of Quinodimethane Derivatives as Precursors for Indigoid Dyes. -Reaction of cyclohexan-1,4-dione with different active methylene heterocycles affords tetrahydroquinodimethane derivatives which are dehydrogenated to targeted indigoid dye precursors (IV)-(VI). Semiempirical calculations indicate that the dehydrogenation stabilizes the system due to the extended conjugation.-(PARDASANI*, R. T.; PARDASANI, P.; ABRAHAM, I.; Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem. 49 (2010) 5, 561-564 ; Dep. Chem., Univ. Rajasthan, Jaipur 302 055, India; Eng.) -H. Haber

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DFT-B3LYP studies have been used to understand the realm of [2 ? 2] photocycloaddition reactions that lead to the formation of four-membered cyclobutane derivatives. Regioselectivity in these reactions has been explored for the typical system 6-amino-2-(3 0 -thienoyl)-1,4-benzoquinone and ethylene. The results favor initial attack of ethylene on quinonoid carbon C5 rather than any other position.

Nonlinear optical (NLO) properties of N-[3-(naphthalene-1-yloxy)butyl]-4-nitroaniline and N-[3-(naphthalene-1-yloxy)butyl]-2,4-dinitroaniline have been calculated theoretically. Theoretical calculations were performed with four different hybrid density functional theories (DFT) i.e. BPV86, B3LYP, LSDA and M-06 with 6-31++G(d,p) basis set. The results showed that these molecular systems have large first static hyperpolarizabilities. Moreover, NLO response of these molecular systems decreased considerably when nitrophenyl is replaced by dinitrophenyl group.