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1.
S.Fazal Hussain M.Tariq Siddiqui G. ManiKumar Maurice Shamma 《Tetrahedron letters》1980,21(8):723-726
Proaporphines undergo light catalyzed rearrangement. Pakistanamine () is thus converted into lumipakistanine (), while pronuciferine () and N-acetylnorpronuciferine () afford the corresponding C-9 hydroxylated aporphines and . Possible biogenetic schemes for the formation of C-8, C-9-, and C-8,9-substituted aporphines are presented. 相似文献
2.
Erythrinin A () has been synthesised by the oxidative rearrangement of dihydropyranochalcone with thallium(III) nitrate (TTN) in trimethyl orthoformate (TMOF) to the dimethyl acetal , followed by cyclisation to , demethylation to and dehydrogenation. Compound could also be obtained from chalcone on similar rearrangement followed by cyclisation, demethoxymethylation and dehydrogenation. In another route, chalcone was oxidatively rearranged with TTN in TMOF, to which on treatment with HCl yielded . 相似文献
3.
The acid catalysed rearrangement of 8-methyl-pentacyclo(5.4.0.02,6.03,10.05,9)undecan-8-endo-o1 () to 3-methyl-(D3)-trishomocuban-4-o1 () provided the key step to the synthesis of the title compound (). 相似文献
4.
Isao Kitagawa Hirotaka Shibuya Hiromichi Fujioka Yoshio Yamamoto Akiharu Kajiwara Kunihiro Kitamura Ayako Miyao Toshio Hakoshima Ken-ichi Tomita 《Tetrahedron letters》1980,21(20):1963-1966
Acid treatment of (IR, 3S,1′S)-1-(1′,2′-Epoxyethyl)-1,2,2-trimethyl-3-acetoxymethyl-cyclopentane ) has been shown to yield three products (, , ), among which and are 1-oxa-bicyclo[3.3.0]octane derivatives formed successive methyl migrations followed by an oxorane ring closure. 相似文献
5.
The 3β-acetoxy-16β,17β-epoxymethyleneandrost-5-ene () transforms into the dihydrooxazine condensed to the sterane skeleton (,,,,,) in a ring-expansion reaction with alkyl and aryl nitriles in the presence of HBF4— diethyletherate The 3β-acetoxy-16α, 17α-epoxymethyleneandrost-5-ene () undergoes a Wagner-Meerwein rearrangement under similar conditions. 相似文献
6.
Paul von Ragué Schleyer Peter Grubmüller Wilhelm F. Maier Otto Vostrowsky Lars Skattebøl Kjetil H. Holm 《Tetrahedron letters》1980,21(10):921-924
Tricyclo(4.2.2.o1,5)decane () in the presence of AlBr3 rearranges partly “forwards” to adamantane () and partly “backwards” to tetrahydrodicyclopentadiene (, largely the oxo isomer). Intermediate , characterizing the →exo-→→→ forward pathway, is found only in small amounts. The detection of a new intermediate, , also shows that a second major rearrangement route from to is being utilized (see dashed lines in Figure 1). 相似文献
7.
Ratna Dasgupta Pranab R. Kanjilal Swapan K. Patra Manish Sarkar Usha Ranjan Ghatak 《Tetrahedron》1985,41(23):5619-5625
The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4--methoxyphenylbicyclo [2.2.2] octan-2-one () and 4--methoxyphenylbicyclo [2.2.2] octan-2-one () from easily accessible starting materials. The carbinol , derived from , undergoes facile rearrangement leading to 1--methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene (), which has been transformed to -1--methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one (). 相似文献
8.
Miyoji Hanaoka Shingo Yasuda Kazuyoshi Nagami Keiko Okajima Takeshi Imanishi 《Tetrahedron letters》1979,20(39):3749-3752
Irradiation of the berberinephenolbetaines (, , and ) effected valence tautomerization to give the 8,14-cycloberbines (, , and ), the aziridine derivatives, in high yield. The 8,14-cycloberbines were efficiently converted to the spirobenzylisoquinolines by regioselective C bond cleavage. 相似文献
9.
Keiichiro Fukumoto Masatoshi Chihiro Yuichi Shiratori Masataka Ihara Tetsuji Kametani Toshio Honda 《Tetrahedron letters》1982,23(29):2973-2976
Thermolysis of a benzocyclobutene derivative () prepared from norcamphor produced stereoselectively a tetracyclic compound (), which was converted to a lactone () having correct stereochemistry at C7, C8, C9, C11, C13, and C14 positions of (±)-klaineanone. 相似文献
10.
A new synthesis of oxindoles () isoquinolones () and benzazepinones () by the intramolecular amidoalkylation of aromatic amides of bismethoxycarbonylaminoacetic acid (, , ) is described. 相似文献
11.
Malvina Farcasiu Edward W. Hagaman Ernest Wenkert Paul von Ragué Schleyer 《Tetrahedron letters》1981,22(16):1501-1504
Unexpected differences in the aluminium bromide-catalyzed rearrangement behaviour of 1,2--trimethylenenorbornane () and its 1,2--isomer () are interpreted. Isotopic labelling studies indicate that reversible abstraction of the tertiary 2- hydride in does not occur. Instead, rearrangement to is favored. The label scrambling in the final product, adamantane (), is attributed to degenerate isomerization in the proto-adamantyl precursor, . 相似文献
12.
Eleven homoerythrina-type alkaloids (-, , ) have been isolated from A. cupressoides (Taxodiaceae), of which six (-, ,) had not previously been reported. 相似文献
13.
The acid catalysed reaction of 4-oxa-homoadamantan-5-one () with benzene yielded a mixture of 4a-phenyladamantan-2-one (), the equatorial isomer' () and 2-phenyl-2,4-o- benzenoadamantane () A plausible reaction pathway for the occurrence of . is put forward. The structure of , was deduced from spectroscopic data and reaction of the proposed intermediate 2,4a-diphenyladamantan-2-ol () with acid. 2,4-o-Ben-zenoadamantane () is prepared likewise. 相似文献
14.
In contrast with the reaction of α-aminonitriles a, the corresponding -acylated α-aminonitriles b-f and oxalyl chloride do not yield pyrazinone derivatives, but 5-aminooxazoles - or 4(5)-imidazolones , the latter being converted in some cases into imidazo [2,1-]isoquinoline-2,5,6(3)-triones. Reactions of compounds b-f and ethyl chlorooxoacetate provide evidence for a 5(4)-iminooxazole intermediate , which aromatizes to yield 5-aminooxazoles -; however, unaromatizable īntermediates of type - isolable as 5(4)y-oxazolones after hydrolysis - undergo a catalyzed Dimroth-type rearrangement to give imidazolone derivatives . 相似文献
15.
Simon J. Edge W.David Ollis Julia Stephanidou Stephanatou J.Eraser Stoddart David J. Williams Kwamena A. Woode 《Tetrahedron letters》1981,22(23):2229-2232
The tri-3-methyltrianthranilide derivatives ()–() have been synthesised. Dynamic 1H n.m.r. spectroscopy indicates that the ,′,″-trimethyl derivative () exists in solution as slowly ring inverting ( ? *) enantiomeric helical conformations. X-Ray crystallography shows that the ,′-dimethyl-″-benzyl derivative () undergoes spontaneous resolution when it crystallises as a 1:1 adduct from toluene. The host molecules adopt a helical conformation (Figure 1) within a lattice structure that contains chiral channels (Figure 2) occupied by guest solvent molecules. 相似文献
16.
The enamino-thione, 1c, reacts with acrylonitrile and 2-chloroacrylonitrile at room temperature to give 3,4-dihydro-4-(1-pyrrolidinyl)-2-thiopyrans, 4 and 5, respectively. The reaction between 1-aryl-3-(1-pyrrolidinyl) (piperidino)-apropene-1-thiones, 1a-c (1d-f), and dimethyl acetylenedicarboxylate gives 4-(1-pyrrolidiny)(piperidino)-4-thiopyrans, 6a-c (6d-f). Compounds 1a-c (1d-f) and ethyl propiolate produce 2-(1-pyrrolidinyl) (piperidino)-2-thiopyrans, 8a-c (8d-f), and a new type of rearrangement is observed. The 2-thiopyran, 9, is formed from 1b and ethyl 3-propiolate, which elucidates the mechanism. 1H and 13C NMR data of 6 and 7 are discussed. 相似文献
17.
Dennis P. Curran 《Tetrahedron letters》1982,23(42):4309-4310
A short, efficient approach to a key chiral intermediate for the synthesis of pseudomonic acids A and C is delineated.Pseudomonic acids A(), B(), and C() are members of a novel of “C-glycopyranoside” antimicrobial agents which have recently attracted synthetic attetion.2 Presently, we wish to report a short efficient stratedy towards the total synthesis of opticaly active pseudomonic acids. The sequence is highlighted by a novel controlled mono-Claisen rearrangement and a highly regioselective π-allylpalladium mediated displacement.Diacetyl-(L)-arabinal ()3 was converted to the bis-ketenesilylacetal and warmed to 60°C according to the Ireland ester-enolate Claisen rearrangement method.4 Over a period of ≈5h, smooth conversion to a major rearranged product was observed by 300 MHz NMR. The identity of was confirmed by direct desilylation and methylation (KF, KHCO3, H2O, HMPA, CH3I). After flash chromatography, compound was isolated in 55% overall yield from . Careful inspection of the crude methylation product revealed the presence of ≈5% doubly rearranged product .The rearrangement of to is a unique example of a selective mono-Claisen rearrangement in which the rate of a second similar Claisen rearrangement ( → ) is much slower under the reaction conditions. Although the reasons for this interesting selectivity are unclear at this time,5 in practice, the mono-Claisen rearrangement obviates the need for selective differentiation of the two hydroxyl groups, a difficult task at best, in this case.Palladium mediated allylic acetate displacement provided an ideal method for introduction of a second chemodifferentiated side chain with allylic retention and retention of stereochemistry. Alkylation of with sodiothylmalonate using 5 mole % Pd(O)dppe26 was unusually facile (<45 min, 25°C, THF). After semi-preparative HPLC, essentially a single regio- and stereoisomer was isolated in 96% yield.7 Structure was confirmed by extensive 1H-NMR decoupling, as well as an off-resonance 13C-NMR experiment. In particular, H1 (δ 4.53) was coupled vicinally to H6 and H6′ (5 Hz, 8 Hz) and H2 (1.5 Hz), and allylically to H3 (2 Hz). In contrast, H4 (δ 2.78) was coupled to H7 (10 Hz), H5e and H5a (1.8 Hz, 4 Hz), H3 (5 Hz), and H2 (<1 Hz). In addition, H1 and H4 exhibited a small long range coupling constant (J = <1 Hz). The coupling constants rule out regioisomer and are fully consistent with the indicated conformation, which minimizes 1,3-diaxial-like interactions.Finally, catalytic osmylation of gave a single cis-diol in nearly quantitative yield. Appending of suitably functionalized side chains to provide an enantiocontrolled synthesis of pseudomonic acids A() and C() is in progress.9,10 相似文献
18.
produces the new dimer kalashine (), together with the previously reported pakistanamine () and pakistanine (). Kalashine is the first aporphine-benzylisoquinoline known to be substituted at C-11. Acid catalyzed rearrangement of pakistanamine () in 3N HCl leads to 1-0-methylpakistanine () together with small amounts of 1-0-methylkalashine () and (+)-armepavine (). Rearrangement of using methanol containing a little 3N HCl gives about equal amounts of and 1,10-di-O-methylpakistanine (). 相似文献
19.
The rate of the thermal rearrangement of (S) 2 chloromethyl-1-ethylpyrrolidine [(S)-1a] to (R)-3-chloro-1-ethylpiperidine [(R) 2a] has been examined at three temperatures in benzene by PMR and polarimetry. The rearrangement was shown to be completely stereospecific and to obey a simple first order rate law. The calculated Ea ΔH3 and ΔS3 were 22 ± 2 (25°), 21 ± 2.5 (25°) and - 10 ± 2 e.u. (0°K) respectively. The effect of solvents having differing dielectric constants was also studied. A transition state 9'a and an ion pair intermediate 3a are suggested for the rearrangement. The stereochemical course of the reactions of (S)-1a, (R)-2a and (S)-2a with hydroxide and methoxide ions have been shown to be 100% stereospecific with an uncertainty of about 1%. The absolute configurations of all optically active reactants and products [(S)- and (R)-4a, (S)-4b (R)- and (S)-5a, (R)-5b, (S,S')-6a, (S,R')-7a and (R,R')-8a] were established by chemical correlations with known compounds or by ORD and chemical inference. The ring opening of both the primary and secondary aziridinium ion positions of 1-azonia-1-ethylbicyclo [3.1.0]hexane [(S)-3a] by nucleophiles proceeds entirely by SN2 processes. The conversion of (R)-1-ethyl-3-hydroxypiperidine [(R)-5a] to (S)-2a. HCl with thionyl chloride in chloroform proceeds by inversion with 4.8% racemization, whereas the thermal rearrangement of (S)-1a to (R)-2a occurs with complete retention of absolute configuration. 相似文献
20.
Terunori Fujita Toshikazu Ohtsuka Harushisa Shirahama Takeshi Matsumoto 《Tetrahedron letters》1982,23(40):4091-4094
Tricyclic epoxide , derived from humulene 6,7-epoxide underwent unusual rearrangement on treatment with TMSOTf to give an apparently methyl group migrated product which was converted to a irregular isoprenoid hydrocarbon Δ8(13)-capnellene. 相似文献