A heteroaromatic compound 3,6-diaminodipyrido[3,2-a: 2′,3′-c]phenazine was synthesized with an improved method to convert 1,10-phenanthroline derivatives to the corresponding 5,6-diones. It was shown that the electron-donating effects of amino substituents were extended not only to pyridine rings but also to the phenazine ring.

The gold(I)-catalyzed cycloisomerization 1,5-enynes and 1,4-allylallenes to tetracyclododecane and tetracyclotridecane derivatives is reported. Complexation of the cationic gold(I) complex to either the alkyne or the allene moiety induces an intramolecular addition of the alkene leading to gold(I)-stabilized carbenoid intermediate. This intermediate undergoes a formal sp 3 -C-H insertion to generate the tertacyclic adduct. A series of deuterium labeling experiments show that the C-H functionalization step proceeds with an inverse kinetic isotope effect.Cationic gold(I) complexes have emerged as powerful π-acids capable of promoting a diverse range of enyne cycloisomerization reactions. 1 In these reactions, the gold catalyst not only serves to activate the alkyne towards nucleophilic addition,2 but also plays a role in stabilizing the cationic intermediates produced in the cyclization event.3 In many of these cases, the stabilization arises from interaction of the gold catalysts with the directly bonded carbocation. 4 Thus, transformations in which these intermediates display reactivity that is reminiscent of electrophilic metal-stabilized carbenes have been developed. 5,6 However, in contrast to other electrophilic metal-carbenoid species, insertion of the gold-stabilized cationic intermediates into sp 3 -C-H bonds is rare. 7,8 We envisioned that access to such a transformation might provide horino@eng.u-toyama.ac.jp, fdtoste@berkeley.edu. With the aim of examining the potential of cationic gold(I)-carbenoid intermediates to participate in this class of reactions, we revisited the gold-catalyzed cycloisomerization of 1,5-enynes A. 10 While we had previously observed that gold-catalyzed cycloisomerizations of cyclobutane and -pentane derived enynes (A, n=1,2) were terminated by a ring expansion to afford C ,10b we postulated that larger more flexible rings might allow for an intramolecular C-H insertion via gold-carbenoid intermediate B (eq 1). NIH Public Access(1)In order to explore this hypothesis, 1,5-enyne 1a possessing cycloheptyl skeleton at the C4 position was allowed to react under our standard conditions (2% (Ph 3 P)AuCl/AgSbF 6 ) for cycloisomerization of 1,5-enynes (eq 2). We were pleased to find that the reaction proceeded smoothly to provide tetracyclic compound 2a in 75% yield after one hour. On the basis the observation that electron donating ligands are preferred for reactions involving trapping of the gold(I)-carbenoid intermediates, we examined N,N-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) and tri(tert-butyl)phosphinegold(I)chloride as catalysts. Gratifyingly, both of these complexes showed improved reactivity (10-15 minutes) in the cycloisomerization reaction and produced 2a in better yield. Notably, in all cases, neither competing deprotonation from gold-carbenoid intermediate B to afford spiro[5.6]dodeca-1,4-diene nor 1,2-alkyl shift to provide ring expansion product (C) were observed.Under these optimized reactions conditions, a number of cycloheptyl or cyclooctyl-substitu...

6,6'-Diamino-2,2'-bipyridine (la) has been found to exhibit a strong fluorescence in the near-UV region. Some amino and/or chloro substituted bipyridines (bpys) have been synthesized and studied to show that only 6-amino-substituted derivatives exhibited a strong emission. The emission of 6-amino-6'-chloro-bpy (3a) was the strongest (A,,, = 429.0 nm; @ = 0.78 in ethanol) among them. On the other hand, little or no emission was observed for monochloro-, dichloro-and 4-amino-derivatives.The application of fluorescent organic compounds to optical devices and photo-functionalized materials is a topic of current interest.' For these uses, the chemical and thermal stability of the compounds are essential factors in addition to their colour and higher emission efficiency. But because of limitations in the modification of existing fluorophores to meet the conditions mentioned above, new series of fluorophores are actively studied.We have been studying the properties and functionality of 6,6'-diamino-2,2'-bipyridine (la) and its derivative^,^-^ and we recently found that l a displayed a relatively strong emission in the near-UV region. 2,2'-Bipyridine (bpy) is a n-electron deficient compound and needs much more drastic conditions than pyridine for both electrophilic and nucleophilic substitution. Though synthesis of its derivatives is rather complicated, the derivatives are inactive for ring-directed reactions and are thermally stable in general. However, relatively little has been known about the fluorescent property of bpy and its derivatives. The bpy derivatives are generally non-fluorescent,' though 3,3'-dimethyl and 3,3'-dihydroxy7 bpys have been reported to show fluorescence.In this report, we describe the fluorescent property of a series of amino-and chloro-substituted bpys at 4-and/or 6-position(s). Among the bpys tested in this study, asymmetrically substituted 6-amino-6'-chloro-bpy (3a) was found to exhibit a remarkably strong emission.

Though the chlorination of an N,N′-annelated phenanthrolinedione, 3,6,7,9-tetrahydro-5H-[1,4]diazepino[1,2,3,4-lmn][1,10]phenanthroline-3,9-dione, gave 2,9-dichloro-1,10-phenanthroline, another dione, 3,5,6,8-tetrahydropyrazino[1,2,3,4-lmn][1,10]phenanthroline-3,8-dione, did not. It demonstrated a simultanous introduction of two chlorine substituents to non-substituted 1,10-phenanthroline via only the former intermediate.