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Benzo Annelation

An evaluation of the effect of benzo annelation on the ease of the Chichibabin reaction in the azine and azole series was made by Doron kin et al. (79CHE218). They related the dependence on time of the total amount of gas evolved as a measure of the activity of the compound. For azine compounds aminated in o-xylene with sodium amide, the activity decreased in [Pg.20]


The Lowest Vertical Ionization Potentials (eV) of Benzo Annelated Heterocycles... [Pg.25]

The benzo-annellated derivative naphtho[l,2-c]furoxan is numbered according to the system (2)] shown. In the literature the name 1,2-naphthofuroxan may often be found, with the same numbering as for a 1,2-disubstituted naphthalene. Although the latter method is perhaps a little clearer to follow, the more systematic scheme (2) will be adhered to in this chapter. [Pg.2]

PPP calculations reproduce the nitro substituent effect and heterocyclic effect on the /,max. For example, the bathochromic shift by substitution of a nitro group is calculated (ca.20nm). It is in good agreement with the experimental value determined (A,max = 598 nm) in toluene. PPP calculation exactly predicts the bathochromic shift by benzo-annelation of the indoline and benzopyran residues (Table 2). In the neutral quinoid form, the calculated charge densities for the ground and first excited states by PPP... [Pg.11]

The synthetic method described in this section can be successfully applied not only to the benzo-annelated thiepins but also to the various kinds of annelated and non-annelated thiepin derivatives. The annelated thiepins thus obtained, though some of them were not isolated, are shown in Scheme 1 491. The thermal stability of these thiepins can be evaluated by their half-lives at an appropriate temperature measured by H-NMR spectroscopy and will be discussed in Section 5.1. [Pg.50]

The photolysis of benzo-annellated quinone diazides such as 2m should preferentially lead to products with intact benzene rings. Monochromatic irradiation... [Pg.189]

A. Prasanna de Silva, H. Q. Nimal Gunaratne, and K. R. A. Samankumara Sandanayake, A new benzo-annelated cryptand and a derivative with alkali cation-sensitive fluorescence, Tetrahedron Lett. 31, 5193-5196(1990). [Pg.46]

It has been predicted that both cations are unstable toward a facile isomerization to a more stable complex HE /CgHg, 38. For the silyl species this was confirmed by fourier transform ion cyclotron resonance (FT-ICR) experiments, which demonstrated that indeed HSi" /C6H6 is formed and not the isomeric trivalent 7-si-lanorbornadienylium. Similarly, it was shown by our group that the 2,3-benzo-annelated 7-silanorbornadienylium 39 undergoes, at ambient temperature in nonpolar solvents, a fast isomerization to the complex PhSi /tetraphenylnaphthalene (TPN), 40, which decomposes yielding TPN as the only detectable product. ... [Pg.166]

Xmax is shifted to 410 nm in 44 (c and g annelation) it is shifted to 422 nm. The explanation of this effect is quite straight forward. Benzo-annelation across a double bond substitutes a bond with half double bond character for a double bond. In terms of the exciton model this decreases both the length of the interacting system and the strength of the interaction. [Pg.58]

Benzo-annelation across a single bond (e.g. b or h) such as in 43 (Xmax = 603 rnn) or in 45 (Xmax = 572 nm) produces bathochromic effects, as a result of the extension of the conjugated system over two additional double bonds. These effects are reproduced quite well by the rr-electron M.O. calculation. ... [Pg.58]

A number of monocyclic and benzo-annelated examples of 1,2- and 1,3-thiazepines have been prepared but there has been little systematic study of these systems. The interesting photochemical interconversions of pyridine N-imides into 1,2- and 1,3-diazepines and of pyridine Af-oxides into 1,2- and 1,3-oxazepines regrettably lack parallels in thiazepine chemistry. There has been more interest in 1,4-thiazepines, as both rearrangement products and possible biogenetic precursors for penicillins and because of the pharmacological value of the benzo- and dibenzo-[l,4]thiazepines as antidepressants and coronary vasodilators. The only review (70ZC361) is excellent but not very recent. [Pg.631]

The scope and limitations of these types of reactions were studied in detail by Hungarian researchers synthesizing a number of derivatives (18) [73ACH(79)113 77JHC583 79ACH( 102)305 82JHC49] [R1 = H, aryl, heteroaryl R2,R3 = H, Me, MeOand benzo-annellation Ar (substituted) phenyl, heteroaryl] the reaction mechanism was also elucidated (Section 1II,B,1). [Pg.162]

A 3-Phosphorin derivatives of benzo annelated rings were intensively studied by Bickel-haupt and coworkers. One of his preferred methods consists in the introduction of the final P=C double bond from appropriate ring systems by basic elimination of HC1 with DBU or other bases. Many benzo-A 3- phosphorins have been reported. An example is the synthesis of 2-phosphanaphthalene (equation 26) (75T1097). Some other examples are shown in (32)-(35). [Pg.507]

Benzo[/]annelated naphtho[bc]thiepine-4-one derivatives 482 are obtained by cyclization of 8-arylmercapto-1 -naphthoic or 1-naphthylmercap-tosalicylic acids 480 and 481 (38M440 75CCC1604 84JHC1737). In the latter case, in order to avoid ortho-acylation, the ortho-position (towards the sulfur atom) of the naphthalene nucleus is blocked by a substituent. [Pg.81]

Leszczynski et al. have shown interest in comparing experimental (matrix isolation) and calculated (B3LYP) IR data (frequency and intensity) to discuss the tautomerism of benzo-annelated pyridonone, pyrazinone, and pyrimidinone (144-148). These equilibria were well reproduced by theoretical calculations carried out at the QCISD and QCISD(T) levels. The combined experimental and theoretical results reveal links between aromaticity and tautomerism. Moreover, a UV-induced phototautomeric reaction transforming the oxo forms into the hydroxy tautomers was observed for all (except 3-hydroxyisoquinoline) studied compounds [144], The interest of Leszczynski in problems related to tautomerism, aromaticity, and proton transfer is also apparent in a study of (lH-aza-hetero-2-ylidene)-acetaldehyde and 2-azahetero-2-yl-ethanol tautomeric pairs [145],... [Pg.178]

Benzodiazepines (1) are the 2,3-benzo-annelated derivatives of 1,4-diazepines. It should be noted that the numbering system for these benzodiazepines proceeds in the opposite direction from that used for the un-annelated diazepines. Therefore, the 1,2,3,4, and 5 positions of the 1,5-benzodiazepines correspond respectively to positions 1,7,6,5, and 4 in the monocyclic compounds. Throughout this chapter the term benzodiazepines refers exclusively to the 1,5-diazo isomers. [Pg.2]


See other pages where Benzo Annelation is mentioned: [Pg.37]    [Pg.164]    [Pg.83]    [Pg.37]    [Pg.58]    [Pg.58]    [Pg.861]    [Pg.165]    [Pg.720]    [Pg.941]    [Pg.957]    [Pg.758]    [Pg.866]    [Pg.89]    [Pg.110]    [Pg.110]    [Pg.205]    [Pg.720]    [Pg.941]    [Pg.957]    [Pg.245]    [Pg.321]    [Pg.91]    [Pg.353]    [Pg.353]    [Pg.354]    [Pg.356]    [Pg.358]    [Pg.358]   
See also in sourсe #XX -- [ Pg.10 ]




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