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1.
《Tetrahedron》1988,44(19):6217-6224
The weak intensity of the CN stretching band in IR spectra for 1-cyanoiso chromenes is obviously determined by the steric position of the CN group in the molecule, as it was established by X-ray structural analysis for the cyanide addition product 2d of 1-isopropyl-3-methyl-2-benzopyrylium salts. Depending on the other substituent in position 1, 1-cyanoisochromenes in aqueous solutions of sodium hydroxide eliminate hydrogen cyanide 2a, b, e, undergo inter-3a, b or intra-mlecular 2c, d recyclisation, or hydrolysis of the cyano group in 2f ; reaction products include α-naphthols 7c, e, β-naphthol 7d, acylchrysenes 5a, b, or the iso chromene-amide 11f , a stable 1-alkylideneisochromene 3e was obtained, and the intermediacy of 3-hydroxy-1-alkylideneiso chromenes was proved by their isolation in the cases of 10c, d 相似文献
2.
《Tetrahedron》1987,43(8):1931-1936
By cycloaddition of nitrilimine and nitrile oxide to diexo and diendo norbornane- and norbornene-fused structural isomeric dihydro-1,3-oxazlnes (1-3), tetracyclic 1,3-oxazino-1, 2,4-trlazolines (7-9) and 1,2,4-oxadiazolines (10-12) were obtained. With norbornehe dipolarophiles, which contain a C=N and a C=C bond, the cycloaddition takes place at the olefinic bond and the diexo compound 4 yields 13 regioselectively, whereas the diendo isomer 5 gives an Isomeric mixture of isoxazolines 14 and 15. From the diexo derivative 6, however, a bis-adduct 16 is formed. The stereostructures of the adducts have been elucidated by NMR spectroscopy. 相似文献
3.
《Tetrahedron》1987,43(17):3987-3995
In the DMSO/NaHCO3 system, 16α-aminomethyl-, 16α-benzylaminomethyl- and substituted benzylaminomethyl-3-methoxy-17β-tosyloxyestra-1,3, 5(10)-triene (3, 5a-k) do not undergo oxidation, but form a tetrahydrooxa-zin-2-one ring (7, 8a-k) via neighboring group participation. Under similar conditions, 16β-aminomethyl-3-methoxy-17β-tosylestra-1,3,5(10)-triene (4) decomposes into 16-methylene-3-methoxyestra-l,3,5(10)-trien-17-one (12). 相似文献
4.
《Tetrahedron》1987,43(8):1827-1834
trans-3-Mesyloxyflavanones 1 were converted into cis- and trans-3-(alkylthio)- and -(phenylthio) flavanones 2-4 by nucleophilic substitution reaction with thiols or thiolates. Flavanones 2-4 were useful intermediates in the synthesis of various sulfur-containing derivatives; flavanones, flavones and dihydrochalcones possessing alkyl- or arylthio, -sulfinyl and -sulfonyl group. Oxidation of cis- and trans- isomers of 4 led to completely different products. 相似文献
5.
Reaction of 3,6-dimethyl-4-phenyl-3,4-dihydrocoumarin5a with anhydrous aluminum chloride gave 3,6-dimethyl-coumarin (6a); likewise, 6-chloro-3-methyl-coumarin (6b) was obtained from5b. Substituted 3-methyl-thiacoumarins (8a,b and 3-methyl-carbostyrils (10a-e) were prepared from the reactions of the respectivea-methyl-cinnamoyl derivatives (7a,b and (9a-e), of thiophenols and anilines. 相似文献
6.
《Tetrahedron letters》1987,28(46):5665-5668
Tricyclic bromoether17, which contained twenty of thirty carbons of thyrsiferol (1d), was synthesized in optically active form starting from trivial compounds2 and3. 相似文献
7.
Summary The following compounds have been obtained and characterized for the first time:O-,m-, andp-ethoxyphenyl-acrylamides and N -methyl-o-, -m- and -p-N-ethoxphenylacrylamides. 相似文献
8.
Lloyd JA Spraggins JM Johnston MV Laskin J 《Journal of the American Society for Mass Spectrometry》2006,17(9):1289-1298
Angiotensin II (DRVYIHPF) and two analogs, (DRVYIAPA and DRVAIHPA), were used as model systems to study the ozonolysis of peptides containing tyrosine and histidine residues. The ESI mass
spectrum of angiotensin II following exposure to ozone showed the formation of adducts containing one, three, and four oxygen
atoms. CID and SID spectra of these adducts were consistent with formation of Tyr+O and His+3O as expected from previous work
with amino acids. However, several fragment ions observed in the CID and SID spectra suggested formation of a rather unexpected
adduct, Tyr+3O, and a small amount of the Phe+O adduct. These findings were confirmed by examining two angiotensin analogs.
Exposure of DRVYIAPA to ozone resulted in the addition of either one or three oxygen atoms on Tyr, while DRVAIHPA showed only the addition of three oxygen atoms—all on His. Other noteworthy minor oxidation products were observed from these
analogs including Tyr+34 Da, His+5 Da, His+34 Da, and His+82 Da. The reaction rates of the peptides with ozone were found
to be similar: second-order rate coefficients are 274 ± 3, 379 ± 6, and 439 ± 34 M−1s−1 for DRVYIAPA, DRVAIHPA, and angiotensin II, respectively. The relative rates indicate (1) an isolated His residue has a slightly greater ozone reactivity
than an isolated Tyr residue, and (2) the reaction rates of isolated residues are not additive when both residues are present
in the same molecule. 相似文献
9.
R. Usha Nanasaheb P. Thakare Shriniwas L. Kelkar Murzban S. Wadia 《Journal of Chemical Sciences》1991,103(2):195-200
Two distinct reaction mechanisms are proposed for the reactions of1,5 and6 with nucleophiles as against those of11,12 and16. The former set undergoes the reactions through carbocation type intermediates2 and3 as efficiently as the stable carbocation4 does, even under similar and very mild conditions. The compounds from the latter group do not form the carbocations under
the same conditions and undergo only direct substitution by strong nucleophiles. 相似文献
10.
K. Nagarajan P. Rajagopalan B. G. Advani V. Ranga Rao G. A. Bhat 《Journal of Chemical Sciences》1992,104(3):383-397
2-Amino-2-arylethylamides1 carrying electron-donating substituents in thepara position are transformed by hot POC13 to the the title compounds2, presumably via iminochlorides 7 and imidazolium derivatives8. Amides lacking this para-substituent give rise to chloroamidines11 under these conditions.m-Methoxyphenethylamide1t and POCl3 form, besides11f, an isoquinoline derivative3. The involvement of an imidazolium compound8 in the formation of ethenamidines has been verified by the synthesis of2a from10. Reaction of amide1w with PCl5 in the cold leads to, besides the chloroamidine11c, thecis-ethenamidine12 which equilibrates with thetrans-isomer2o in hot toluene. Thienylethyl urea13 converted by hot POCl3 to the imidazoline16, while phenylpropylamide17 forms only the iminochloride18a.
Contribution No. 752 from Research Centre 相似文献
11.
S. Narayanaswami S. Rajeswari B. R. Pai K. Nagarajan W. J. Richter S. J. Shenoy 《Journal of Chemical Sciences》1984,93(2):145-155
Solutions of 3,4-dihydro-6,7-methylenedioxyisoquinoline (1) and analogues2–5 and9 as well as isoquinolines7 and8 in certain samples of CDCl3, CCl4, DMSO-d6 or acetone-d6 gave rise to anomalous1Hnmr spectra with extreme line broadening, signals due to protons at C-l and C-3 most often not being seen. The spectra of1 and3 were most striking in this respect.1Hnmr spectra of the quaternary salt10 and the model schiff base11 were normal. Several hypotheses for the observed line broadening have been considered and rejected, a slow equilibrium1 ⇆13 being one of them. NaBH4 reduction of1 and2 followed by mass spectrometric analysis of the crude tetrahydroisoquinolines16 and17 ruled out a slow equilibrium1 ⇆14 and2 ⇆15 as contributory cause for line broadening. The crude reduction products unexpectedly contained N-ethyl species22 and25. Their formation is rationalised 相似文献
12.
K. Nagarajan A. Nagana Goud V. Ranga Rao R. K. Shah S. J. Shenoy 《Journal of Chemical Sciences》1992,104(5):549-568
Cyclization of N-(2-haloacyl)-8-hydroxy-l,2,3,4-tetrahydroqumolines4–7 and9 with alkali affords pyridobenzoxazinones21–24 and26 respectively and of the 4-chlorobutyramide13 with NaH, the benzoxazocinone31. Exposure of 3-chloropropionamide12 to NaH affords acrylamide15, benzoxazepinone28 or methyl benzoxazinone22 or mixtures thereof under various conditions.28 undergoes rapid base-catalysed ring contraction to22. NaH-catalysed ring closure of acrylamide15 affords mixtures of22 and28, while from the crotonamides16 and17, the methylbenzoxazepinones29 and30 are obtained preponderantly, the former amide yielding only traces of the ethyl benzoxazinone23.29 shows no propensity for ring contraction to give23. The cinnamoyl derivatives18,19 and20 are cyclized to benzyl benzoxazinones24,27 and25, respectively. The intermediacy of the phenyl benzoxazepinone39 in the formation of24 has been established by deuteration studies. Benzylidene benzoxazinone41 is obtained from dibromocinnamamide14 and propiolamide40. Dichloracetamides8 and10 undergo interesting ring closure to compounds45–54 upon treatment with amines. The course of electrophilic reactions of the lactams depends upon the ring size.
Contribution No. 18 from Searle R & D Centre
Presented at a symposium to felicitate Prof N S Narasimhan at the University of Poona, November 18–19, 1988 相似文献
13.
Thomas F.O. Lim Jerry K. Myers Greg. T. Rogers Paul Ronald Jones 《Journal of organometallic chemistry》1977,135(2):249-259
The regioselectivity of the hydroboration of the methylchlorovinylsilanes, ClnMe3?nSiCHCH2 (n= 0 ? 3), has been investigated using BH3←THF, 9-BBN, disiamyl- and dicyclohexylborane. Methylation of the adducts with methylmagnesium bromide is complicated by formation of tetraalkylboronates. Alkaline hydrogen peroxide oxidation of the boronates gives reasonable yields of the corresponding α- and β-trimethylsilylethanols forn= 0 and 1. Forn= 2 and 3, conversion of the adducts to the corresponding α- and β- deuteroethylsilanes by treatment with excess sodium methoxide in methanol-0-d provides a more effective means of derivatization. Addition of the alkenes,n= 2 or 3, to excess BH3←THF givesca. 90% of the α-boro-organo-chlorosilanes. For all of the alkenes, the dialkylboranes giveca. 80% of the β-boron adducts. 相似文献
14.
V. A. Maslennikova G. L. Genkina R. U. Umarova A. M. Navruzova N. K. Abubakirov 《Chemistry of Natural Compounds》1968,3(3):143-146
Summary The cardenolides of six species ofErysimum and ofSyrenia siliculosa have been studied. The cardiac glycosides erysimin and erysimoside have been found inE. altaicum, E. marschallianum, E. nuratensae, andS. siliculosa. In addition to these glycosides,E. diffusum has yielded desglucocheirotoxin, canescein, and a new cardenolide, erydiffuside,E. violascens has yielded gypsobioside, andE. cuspidatum has yielded a new glycoside cuspidoside.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 2, pp. 173–178, 1967 相似文献
15.
Karsten Krohn Michael Klimars Hans-Ju¨rgen Ko¨hle Eckehardt Ebeling 《Tetrahedron》1984,40(19):3677-3694
7,10-O-Dimethyl- ζ -pyrromycinone (78) and the not naturally occurring 7-deoxyanthracyclinones 76 and 77 are prepared via base itinduced cyclization of the ketoesters 73 - 75, and stereoselectively hydroxylated to the 2,4-cis diol 83 and 85. 相似文献
16.
Euchrenone a2 (7) isolated from the roots ofEuchresta japonica has been synthesised from 3-prenylphloroacetophenone (1) by other workers. We carried out its cyclodehydrogenation with dichloro dicyano quinone (DDQ) to obtain 6-acetyl-5,7-dihydroxy-2,2-dimethylchromene
(2) which was ethoxymethylated in the 7-position to give 6-acetyl-7-ethoxymethoxy-5-hydroxychromene (3). Chalcone condensation of3 and 4-ethoxymethoxy-3-C-prenylbenzaldehyde (4) gave 4,6′-bisethoxymethoxy-2′-hydroxy-6″, 6″-dimethyl-3-C-prenylpyrano (2″, 3″–4,3) chalcone (5) which cyclised with methanolic sodium acetate to give protected 5,4′-bisethoxymethoxy-6″, 6″-dimethyl-3′-C-prenylpyrano (2″, 3″–7,8) flavanone (6). Deprotection of6 with 4% methanolic HCl yielded (7) with melting point and spectral data identical to that of the natural compound. 相似文献
17.
Reaction of sodium 2-formylbenzenesulphonate (1) with thionyl chloride or phosphorous pentachloride gives a mixture of pseudo (2) and normal (3) sulphonyl chlorides. Whereas ammonium 2-carboxybenzenesulphonate (6) gives only the normal sulphonyl chloride (7) on reaction with thionyl chloride, a mixture of normal (7) and pseudo (8) isomers are formed on reaction with phosphorous pentachloride. Sodium 2-benzoylbenzenesulphonate (15), on the other hand, gives the corresponding normal sulphonyl chloride (16) on reaction with both of the reagents mentioned above. Based on these observations it is concluded that γ-keto sulphonic
acids are amenable to the influence of γ-carbonyl group as in the case of γ-keto carboxylic acids but to a lesser extent. 相似文献
18.
V. Balasubramaniyan P. Balasubramaniyan M. J. Wani 《Journal of Chemical Sciences》1991,103(5):621-629
Maleimides (2a−j) react with thiourea in refluxing ethanol to yield the corresponding N-aryl α-(2,3,4,5-tetrahydro-4-oxo-l,3-thiazole-5-yl)
acetamides (6a−j) in 72–85%. The spectral and analytical data are consistent with the assigned structures for6a−j. Under similar conditions, isomalemides (3a−b and3d−f) furnish the corresponding6a−b and6d−f in 76–86%. While maleanilic acid (4a) itself failed to react with thiourea,4b−ē,4i and4j yielded a mixture of the corresponding6b−ē,6i and6j in 2–50% and fumaranilic acids (7b−ē,7i and7j) in 50–80%. Methyl maleanilates (5b,5d−f and5i) gave6b,6d−f and6i in 78–85%. The reaction course of Raney nickel desulphurisation of6a−b,6d,6f and mass spectral fragmentation of6b support the assigned structures.
Part XXI 1991 Org. Prep. Proc. Inter. (in press) 相似文献
19.
V. K. Basenko A. N. Berlizov R. H. Filby I. A. Malyuk V. V. Tryshyn 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(2):353-361
The paper contains a summary of the recent developments of the prediction part of the NAAPRO (Neutron Activation Analysis PRognosis and Optimization) code. Specific details are given for the activation product yield calculation approach used in the program and
for the nuclear data libraries. The prospects for the code development are discussed. 相似文献
20.
《Tetrahedron letters》1987,28(46):5661-5664
The stereostructures of (Z)-tarchonanthuslactone (2) and the δ-lactone of (Z)-5, 7, 9, 11-tetrahydroxyhexacos-2-enoic acid (3) were established as9 and27 by the stereoselective syntheses of authentic9 and26 (triacetate of3), respectively. 相似文献