摘要:

Diazo‐Group Transfer to Amino‐arenes and Amino‐hetarenes Using Azidinium Salts: Synthesis of 1, 2, 3‐TriazolesDas Azidiniumsalz 2‐Azido‐3‐äthyl‐benzthiazolium‐tetrafluoroborat (1) lässt sich als Diazogruppenüberträger auf Amino‐arene und Amino‐hetarene einsetzen. Die primär entstandenen Diazoniumsalze cyclisieren sich zu kondensierten ν‐Triazolen bzw. kuppeln mit den Edukten z

ISSN:0018-019X    

DOI:10.1002/hlca.19780610112

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Synthesis of 4‐amino‐ and 4‐hydroxy‐3‐(p‐chlorophenyl)‐valeric acids. X‐ray structure of cis‐4‐(p‐bromophenyl)‐5‐methyl‐2‐pyrrolidinoneThe syntheses of diastereomeric 4‐amino‐ and 4‐hydroxy‐3‐(p‐chlorophenyl)‐valeric acids and of their ring closure products (lactones and lactams), starting from 3‐(p‐chlorophenyl)‐4‐oxo‐valeric acid, are described. A single‐crystalX‐ray structure analysis ofcis‐4‐(p‐bromophenyl)‐5‐methyl‐2‐pyrrolidinone is given. Some aspects of the bio

ISSN:0018-019X    

DOI:10.1002/hlca.19780610113

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Preparation of styryl derivatives of 2‐phenyl‐imidazo [1, 2‐a]pyridine2‐(p‐Tolyl)‐imidazo [1, 2‐a]pyridines and 7‐methyl‐2‐phenyl‐imidazo [1,2‐a]‐pyridines can be converted, in dimethylformamide, on reaction with anils of aromatic aldehydes in the presence of potassium hydroxide or potassiumt‐butoxide, into the corresponding 2‐(stilben‐4‐yl)‐ and 2‐phenyl‐7‐styry1‐imidazo [1, 2‐a]‐pyridines (‘Anil‐Synthesis’). The 2‐(p‐tolyl)‐imidazo [1,2‐a]pyridines react far le

ISSN:0018-019X    

DOI:10.1002/hlca.19780610114

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

Preparation of styryl derivatives of 2‐phenyl‐4H‐1,2,4‐triazolo [1,5‐a]pyridine7‐Methyl‐2‐phenyl‐ and 2‐(3‐chloro‐4‐methylphenyl)‐4H‐1,2,4‐triazolo[1,5‐a]‐pyridines react with anils of aromatic aldehydes in the presence of dimethyl‐formamide and potassium hydroxide at 20–45° to yield the 2‐phenyl‐7‐styryl‐ and 2‐(2‐chloro‐stilben‐4‐yl)‐4H‐1,2,4‐triazolo [1,5‐a]pyridines respectively (‘Anil Synthesis’). Further, theSchiff's bases derived fromo‐chloroaniline and 2‐(p‐formyl‐phenyl)‐ and 7‐formyl‐2‐phenyl‐4H‐1,2,4‐triazolo [1,5‐a]pyridine yield, with methyl‐ and withp‐tolyl‐s

ISSN:0018-019X    

DOI:10.1002/hlca.19780610115

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractUsing the Frozen Core (FC) MO procedure described in a previous communication, we have computed the long‐wavelength chiroptic properties of oligopeptides in the parallel‐chain (PC) pleated sheet conformation, in the poly (L‐proline)Iand poly (L‐proline)IIconformations. The main features of the computed results are: (a) In the PC pleated sheet conformation the π–π* transition with the highest positive rotatory strength appears at shorter wavelength than the π–π* transition with highest negative rotatory strength and is polarized mainly perpendicularly to the chain axis. There is an analogy between the computed PC pleated sheet spectrum and that calculated for a cyclohexapeptide of low symmetry, in a conformation which is probably stabilized by intra‐annular hydrogen bonds. (b) In the polyproline I conformation the computed π–π* transition with highest positive rotatory strength is also the longest‐wavelength π–π* transition and is polarized mainly along the helix axis. There is an analogy between this spectrum and that calculated for cyclo(tri‐L‐proline) of symmetryC3. (c) The poly‐prolineIICD. spectrum may be qualitatively reproduced only by invoking very strong n – π interaction. The local n –π mixing parameter Λ must take on values ⪖3 eV, which is of the order of a nearest‐neighbor core resonance integral between atomic 2p orbitals of same spatial orientation. The question concerning the structural reasons for this situation is raised. As far as comparisons with experimental data are

ISSN:0018-019X    

DOI:10.1002/hlca.19780610116

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractThe triplet‐triplet absorption spectra ofp‐N, N‐dimethylnitroaniline, 4‐nitro‐p‐terphenyl, 1‐amino‐4‐nitrofluorene, 5‐nitroacenaphthene,trans‐1‐(4‐methoxy‐phenyl)‐2‐nitroethylene (MeONS), andtrans‐1‐(4‐dimethylaminophenyl)‐2‐nitroethylene (DANS) in EPA glass at 77 K are reported, together with molar extinction coefficients and PPP‐SCF‐MO‐CI calculations. The two nitrostyrenes, MeONS and DANS, have been examined in fluid media at room temperature using nanosecond laser photolysis, and their triplet lifetimes found to increase substantially with increase in solvent polarity and charge‐transfer character of the compound. This is interpreted in terms of the diradical/zwitterionic nature of the triplet state affecting the T1–S0energy gap at the 90° twisted configuration of the olefinic linkage.The decrease in both the triplet yield and the fluorescence yield of DANS with increase in solvent polarity is explained by the intervention of an internal conversion process involving a rotation of the dim

ISSN:0018-019X    

DOI:10.1002/hlca.19780610117

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractDelayed fluorescence (DF.) spectra of 1,2‐benzanthracene, fluoranthene, pyrene, and chrysene in methylcyclohexane were measured at −80° up to the wavenumber corresponding to the energy of two triplets. With all four compounds a weak DF. Sn→ S0from the highest state Snaccessible by triplet‐triplet annihilation (TTA) was found. Lifetimes of Sncalculated (a) from the ratio of the DF's Sn→ S0and S1→ S0and (b) from the difference in line‐width of the 0,0‐transitions Sn,0← S0,0and S1,0← S0,0agree reasonably well. This indicates that population of the highest accessible excited singlet state is the dominating primary process in the excited singlet channel ofTTA.There is no evidence for excimer formation being the first step inTTA. DF.spectra extend up to the energy of two triplets. With pyrene the intensity distribution in the hot‐band region of the DF. S2→ S0suggests that inTTAthe same vibrational selection rules are valid as in one‐photon absorption S2← S0and that vibrational relaxation within the S2manifold is slow compared with internal conversion S2↝ S1. The experimental technique is described in detail and experimental difficulties arising from impurities and photop

ISSN:0018-019X    

DOI:10.1002/hlca.19780610118

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

AbstractDuring UV.‐irradiation of aliphatic carboxylic acids and esters in aqueous and nonaqueous solutions various alkyl and acyl type radicals derived from parent compounds and solvents have been observed by ESR.‐spectroscopy. The structures of the radicals point to α‐cleavage, β‐dehalogenation and photoreduction as major photolytic processes of carboxylic acids and esters. The relative contributions of these processes to the overall photodecompositions depend on the carboxyl substituents, on solvent and temperature. Similarities of carboxyl and carbonyl group photochemistry are

ISSN:0018-019X    

DOI:10.1002/hlca.19780610119

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

On the Mechanism of Radiationless Deactivation of the First Excited Singlet State of 2‐Alkyl‐indazolesThe temperature dependence of the quantum yields of fluorescence (ΦF), intersystem crossing (ΦT) and photoreactions (ΦR) have been measured for several neutral and protonated 2‐alkyl‐indazoles. The experimental data (Fig. 1and3) can be interpreted in terms of the reactionschemes 1and2with temperature independent constants for fluorescence emission and intersystem crossing and temperature dependent photochemical primary processes. Whereas at low temperatures the sum of the quantum yields of fluorescence and intersystem crossing equals 1, at higher temperatures a very efficient radiationless deactivation process takes place(Table). Based on kinetic and photochemical data it is concluded that this deactivation proceedsviaa hypersurface crossing(Fig. 2)or hypersurface touching(Fig. 4)in the course of the photochemical rearrangements1→2and4→5respectively.Similar mechanisms are expected to be responsible for the unusual internal conversion in other heterocy

ISSN:0018-019X    

DOI:10.1002/hlca.19780610120

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY

摘要:

The Synthesis of Actinioerythrol, Violerythrin and other 2,2′‐Dinor‐carotenoids2,2′‐Dinor‐carotenoids including the naturally occurring actinioerythrol (1) and the blue carotenoid violerythrin (2), as well as 2,2′‐dinor‐rhodoxanthin (25) and 2,2′‐dinor‐zeaxanthin (27) and others have been obta

ISSN:0018-019X    

DOI:10.1002/hlca.19780610121

出版商:WILEY‐VCH Verlag GmbH    

年代:1978

数据来源: WILEY