Addition of functionalized organolithium reagents to p-benzoquinones and cyclohexadienones: synthesis of functionalized cyclohexadienones, dienols and dienediols

Heterocyclic Quinol-Type Fluorophores: Synthesis, X-ray Crystal Structures, and Solid-State Photophysical Properties of Novel 5-Hydroxy-5-substituent-benzo[b]naphtho[1,2-d]furan-6-one and 3-Hydroxy-3-substituent-benzo[kl]xanthen-2-one Derivatives

Novel heterocyclic quinol-type fluorophores (4 a-c) and (5 a-c) that contain substituents (R = Me, Bu, Ph) with nonconjugated linkages to the chromophore skeleton have been synthesized and their photophysical properties have been investigated in solution and in the solid state. Considerable differences in the absorption and fluorescence spectra were observed between the two states. Quinols 4 a-c and 5 a-c exhibited almost the same absorption and fluorescence spectra in solution; however, their solid-state fluorescence excitation and emission spectra in the crystalline state were quite different. We performed X-ray crystallographic analyses to elucidate the dramatic effect of the substituents of the nonconjugated linkage on the solid-state fluorescence excitation and emission spectra. The relationships between the solid-state photophysical properties and the chemical and crystal structures of 4 a-c and 5 a-c are discussed on the basis of the X-ray crystal structures.

New cyclohexadienone derivatives: preparation and chiral discrimination in high-pressure Diels-Alder cycloadditions

A wide range of cyclohexadienones has been synthesised in order to study their reactivity and their regio- and stereoselectivity with the enantiopure diene 1 under high-pressure conditions. Computational investigations were used to point out some parameters which affect the reactivity in this high chiral discrimination process. In addition, the resulting [4+2] cycloadducts allowed the preparation of new polyfunctional cyclohexenone derivatives.

A new synthesis of p-hydroxy phenylglycine and some analogues from p-benzoquinone

[reaction: see text] A new route to p-hydroxy phenylglycine and N-substituted analogues has been developed starting from p-benzoquinone. 1,2-Addition of methyl lithioacetate to p-benzoquinone and subsequent quenching of the oxygen anion with methyl chloroformate, followed by an elimination-addition reaction with an appropriate amine, resulted in the desired amino acid derivatives. A diastereoselectivity of 60% was achieved using 8-phenylmenthyl acetate as the chiral auxiliary.