摘要:

AbstractThe 10‐, 11‐, 19‐ and 20‐mono‐13C‐all‐trans‐retinals were synthesized with>98% chemical purity and 92%13C incorporation from13C‐labelled acetonitrile and13C‐labelled methyl iodide. Their13C‐13C and13C‐1H NMR coupling

ISSN:0165-0513    

DOI:10.1002/recl.19831020701

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe biliverdin model compound1could be prepared in high yield by acid‐catalyzed condensation of 3,4‐dimethyl‐2,2′‐pyrromethen‐5[1H]‐one (9) with the novel 3,4‐dimethyl‐5′–formyl‐2,2′‐pyrromethen‐5[1H]‐one (11). The biliverdinium model compound 3 could analogously be prepared quantitatively from 1′,3,4‐trimethyl‐2,2′‐pyrromethen‐5[1H]‐one (10) and 5′‐formyl‐1′,3,4‐trimethyl‐2,2′‐pyrromethen‐5[1H]‐one (12).The analytical, chemical, photochemical and photophysical properties of these model compounds have been investigated. The data so obtained ar

ISSN:0165-0513    

DOI:10.1002/recl.19831020702

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe barrier to the ring inversion of the title compound has been determined using dynamic13C NMR: ΔG≠253= 47.9 kJ·mol−1. Empirical force field calculations show that the (half‐chair)chair(half‐chair) ground state inverts in two equi‐energetic steps via the (half‐chair)‐twist(inverted half‐chair) conformer. The calculated ΔH≠is 46.2 kJ·mol−1usingAllinger's MM2 and 41.7 kJ·mol−1usingWh

ISSN:0165-0513    

DOI:10.1002/recl.19831020703

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe photochemistry of1band2b,i.e.the valeryl analogues of (E)‐α‐ (1a) and (E)‐β‐ionone (2a), respectively, has been studied.Upon irradiation with λ 254 and 300 nm, the α‐isomer1bexhibits the same reactions as the parent ionone1a,viz.(E)‐(Z) isomerization, followed by photo‐deconjugation and subsequent α‐cleavage with formation of the 1,3‐ and 1,5‐acyl shift isomers. Upon irradiation of the β‐isomer2bwith λ 254 nm, only the α‐pyran isomer15is formed, although extensive polymerization does occur. Neither the α‐ nor the β‐isomer yields any detectable product resulting from a Norrish type II reaction in which the γ

ISSN:0165-0513    

DOI:10.1002/recl.19831020704

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractTreatment of 3‐nitro‐1,6‐naphthyridine, its 2‐chloro‐, 2‐ethoxy‐ and 2‐amino derivatives, with liquid ammonia, containing potassium permanganate, gave the corresponding 2‐X‐4‐amino‐3‐nitro‐1,6‐naphthyridines (X = H, Cl, OEt, NH2). From1H NMR spectroscopy sound evidence for the intermediacy of 2‐X‐4‐amino‐1,4‐dihydro‐3‐nitro‐1,6‐naphthyridine is obtained. Similarly, from 5,8‐dichloro(dibromo)‐1,7‐naphthyridine, the corresponding 2‐amino‐5,8‐dichloro‐(dibromo)‐1,7‐naphthyridines were formed on treatment with liquid ammonia/potassium amide/potassium permanganate.1H

ISSN:0165-0513    

DOI:10.1002/recl.19831020705

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractPhotolysis of 4‐R‐1,4(or 3,4)‐dihydropyrimidines causes ring contraction into imidazoles, provided that the substituent R is capable of sufficiently stabilizing an anionic centre (R = 2‐thiazolyl, 2‐pyridyl, 4‐pyridyl). Chemical evidence is presented to show that the ring contraction of 6‐phenyl‐4‐(2‐pyridyl)1,4(or 3,4)‐dihydropyrimidine occurs via heterolytic fission of the C(1)‐C(6) bond of intermediate 1‐phenyl‐6‐(2‐pyridyl)‐2,4‐diazabicyclo[3.1.0]hex‐2(or 3)‐ene. The anion‐stabilizing effect of R is correlated with the acid strength (pKa) of R–CH3. A pKavalue around 30 probably determines the border‐line between ring contraction into an imidazole and formation of

ISSN:0165-0513    

DOI:10.1002/recl.19831020706

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractDuring a study on the amination of 4‐phenylpyrimidine in potassium amide/ liquid ammonia it was found that the extent to which theSN(ANRORC) mechanism operates in the amination largely depends upon whether an ammonium salt is used in quenching the reaction. The composition of the σ‐adduct mixture, the structure of the open‐chain intermediates, the inhibition of theSN(ANRORC) mechanism and the course of the amination in apolar solvents have been investigated. In addition, it has been found that, in the amination of 4‐tert‐butylpyrimidine, theSN(ANRORC) mechanism occurs to only a very limi

ISSN:0165-0513    

DOI:10.1002/recl.19831020707

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractNitriles R–CH2CN where R is CN, SO2C6H5, C6H4‐NO2‐p, C6H4‐CF3‐m, are effective reagents for converting 5‐nitropyrimidine (1) into 2‐amino‐5‐nitro‐3‐R‐pyridines (7). In reactions of1with cyanoacetic acid derivatives (methyl, ethyl,tert‐butyl esters), 3‐cyano‐5‐nitro–2(1H)‐pyridone is formed in addition to7.Ketonic nitriles, such as 3‐oxobutyronitrile and 3‐oxo–3‐phenylpropionitrile, react with1to form 2‐methyl‐ and 2‐phenyl‐5‐nitro‐3‐cyanopyridine, respectively.Plausible mechanisms are discussed. The reaction of1withN‐(cyanoacetyl)carbamate provides a facile synthetic route to

ISSN:0165-0513    

DOI:10.1002/recl.19831020708

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe smooth conversion of the readily available compounds, H2C=C(OMe)‐CR2′‐X (1; X = OC(O)Me or OS(O)Me), with R‐ZnCl reagents, using Pd[PPh3]4as catalyst, is described. It is shown that via this route several 3‐methoxy‐1,3‐dienes H2C=C(R)‐C(O)Me)=CR2′ (2), in which the group R is 1‐alkenyl, aryl, 1,2‐alkadienyl or 1‐alkynyl, can be prepared. The results obtained with R‐Cu or R2CuM were generally inferior to those foun

ISSN:0165-0513    

DOI:10.1002/recl.19831020709

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY