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1.
The formation of the -bicyclo [6.1.0] nona-2,4,6-trienes - is not due to the sequence → → , which would involve the symmetry-forbidden reaction → even at ?50°C. Rather, reaction of RX at C4–7 of , which is formed together with , leads (probably via - and - to -. 相似文献
2.
The synthesis of trifluoromethylvinylketone is described. The metal hydride reduction of ethyl trifluoroacetoacetate gives the glycol . Selective tosylation of occurs on the primary hydroxyl group and leads to . Tosyl-chloride exchange produces the chlorohydrin which is oxydized to the β chloroketone . The dehydrohalogenation of leads to the fluorinated ethylenic ketone . 相似文献
3.
Géza Stájer LászlÓ Mód Angela E. Szabó Ferenc Folöp Gábor Bernáth Pál Sohár 《Tetrahedron》1984,40(12):2385-2393
The -- amino acid with norbornene skeleton was converted into 2-aryvl---1,3-oxazin-4-ones -. These compounds, similarly to the isomers - studied by us earlier, undergo retrodiene decomposition under mild conditions to give 2-aryl-6-l,3-oxazin-6-ones (-) in 50-60% yield. The ratio of the decomposition rate constants of the tricyclic and -1,3-oxazin-4-ones, measured in toluene solution, is about 2. 相似文献
4.
Aziridines react with trifluoromethyl hypofluorite at ? 40°C to produce mixtures of 1-(aziridine)carbonyl fluoride and 1-fluoroaziridine , the proportions of which depend on steric effects. Several compounds react with starting materials to give 1, 1′-(carbonyl)bisaziridines . Most compounds and all compounds are isolated. Chemical properties and ir and nmr data of , , are described; the formation of an isocyanate and a substituted urea from a compound is observed. A mechanism for this reaction is suggested. 相似文献
5.
《Tetrahedron》1986,42(18):5081-5088
5-Ethoxycarbonylmethylene-cyclooctanone () is prepared by Wittig monoolefination of dione with phosphorus ylide . Thermal transannular cyclization of oxime and phenylhydrazone of the ketone affords 3-oxa-2-aza- and 2,3-diaza[3.3.3] propellanes and respectively. Irradiation of ketone , its oxime , and its dimethylhydrazone furnish 9-oxa-, and 9-aza[3.3.2] propellanes , , and , respectively. In addition to the propellane , phenylazobicyclo compound is also obtained from phenylhydrazone . The acetyl derivatives and of propellanes and are also prepared and studied. 相似文献
6.
Michel Lebœuf Diego Cortes Reynald Hocquemiller André Cavé Angèle Chiaroni Claude Riche 《Tetrahedron》1982,38(19):2889-2896
The structure of guoregine, a new isoquinoline alkaloid from , Annonaceae, has been deduced by spectral analysis and confirmed by an X-ray structure determination. It is the first member of a new class of cularine-related alkaloids (α--dimetyltetradehydrocularines). 相似文献
7.
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
8.
The synthesis of - and -N-(4-amino-3, 3-dimethyl-2-hydroxybutyryl)- β-alanine () is described. Compound is an analog of pantothenic acid in which the 4′-hyroxy group is replaced by amino group. The synthetic sequence leading to involved the synthesis L-4-amino-3,3-dimethyl-2-hydroxybutyric acid and its resolution. Coupling of N-benzyloxycarbonyl N-hydroxysuccinimide ester () with β-alanine and followed by removal of the protecting group gave . 相似文献
9.
Trifluoroethyl cyclohexyl ketone () is prepared by acylation of difluoroethylene () with cyclohexanecarboxylic acid chloride (), followed by Cl→F exchange with potassium fluoride in the presence of triethylbenzyl- ammonium chloride. Bayer-Villiger oxidation of ketone () with trifluoroperacetic acid gives cyclohexyl trifluoropropionate (). 3,3,3-trifluoropropionic acid () is obtained by treatment of () with trimethylsilyl iodide. Condensation of 2,2,2-trifluorodiazoethane () with ethyl glyoxylate () gives mainly ethyl 4,4,4-trifluoro-2-ketobutyric acid ester () which leads after hydrolysis to the corresponding acid (). 相似文献
10.
The retroaldol-aldol isomerization of the epimeric hydroxyketones and was found to yield predominantly and , respectively, under kinetic conditions in the presence of chelating lithium cations. In hydroxylic medium is the preferred kinetic product. Under equilibration conditions and predominate. 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.
Two cleavage products, -dimethylmuconate () and -dimethyl-muconate (), are inefficiently produced in the 9,10-dicyanoanthracene (DCA) sensitized photooxidation of -dimethoxybenzene (-DMB) in polar solvents. An electron transfer mechanism is proposed in which superoxide ion (O?20 combines with ortho-dimethoxybenzene to form a dioxetane (3), which cleaves to form (). The initial products is , which is rapidly converted to and other products under the conditions; cis-trans isomer is formed. 相似文献
13.
Gábor Blaskó Natesan Murugesan Alan J. Freyer Daniella J. Gula Bilge Şener Maurice Shamma 《Tetrahedron letters》1981,22(33):3139-3142
Stereoselective rearrangement of indenobenzazepine cis ketols and with TPAA in pyridine produces spirobenzylisoquinolines and , respectively. The latter product is also obtained by rearrangement of trans ketol . The transformation of ketols and must, therefore, proceed through the intermediacy of aziridinium cation . A similar process obtains in the transformation of to . NaBH4 reduction of gives (±)-raddeanine (). Rearrangement of diol supplies directly. (±)-Yenhusomine () is obtained from the reamangement of either diol, or . In like fashion, diols and supply spirobenzylisoquinoline . 相似文献
14.
Flow vacuum thermolysis (FVT) of thiophene-2,3-dicarboxylic anhydride () in the presence of 2,3-dimethylbutadiene () gives, in addition to 5,6-dimethylthianaphthene (). small quantities of a dihydrodimethylthianaphthene () and another dimethylthianaphthene () which is probably also formed by dehydrogenation of with chloranil. The partial structures of these minor products are consistent with their being formed by a [2+2]-cycloaddition between and an intermediate aryne, 2,3-didehydrothiophene (), followed by a rearrangement of the resulting adduct and dehydrogenation. FVT of in the presence of 2,5- () or 3,4-dimethylthiophene () also gave a mixture of the dimethylthianaphthenes (, ) which can be rationalized as arising by a [4+2]- and two [2+2]-cycloadditions of the aryne to the thiophenes with subsequent desulfurization. The lack of equilibration of the products , and , was demonstrated and their origin as a function of the structure and reactivity of the aryne discussed. 相似文献
15.
Details of a novel radical-initiated polyolefinic cyclization approach to linear condensed cyclopentanoids are reported. The strategy is executed in three stages: (1) Sn2′-anti opening of a vinyl lactone to produce a trans-3,5-disubstituted cyclopentene, (2) rapid elaboration to a cyclization precursor, and (3) single step tandem radical cyclization to produce a cis-anticis tricyclo[3.3.0]undecane. Model substrates and give high yields of tricyclic products and , respectively. An effort to rationalize the interesting endo selectivity via the Beckwith transition state model is proposed. Cyclizations of and to and demonstrate the viability of a tandem hexenyl-hexynyl cyclization. The work culminates with a total synthesis of (±)hirsutene. A selective approach to methyl substituted vinyl lactones by Claisen rearrangement-phenylselenolactonization-elimination of acetoxy cyclopentenols is exemplified by the synthesis of . Tandem cyclization of produces hirsutene () in a single step. Alternatively, cyclization of yields trimethylsilyl hirsutene. 相似文献
16.
The citromycinone-derivatives and have been obtained by intramolecular Marschalk cyclisation of α-hydroxyaldehyde . An unexpected opening of epoxide to -diol was observed. By exclusion of the alternative formula structure is proposed for α-citromycinone. 相似文献
17.
Deprotonation of chloromethyleniminium chlorides (, ) leads to cis-trans-isomeres 1,2-diamino-1,2-dichloro-ethenes (, resp. , ); their reactivity is described. 相似文献
18.
《Tetrahedron》1986,42(8):2345-2350
In the reactions of 2-thioxo-- and -3,1-perhydrobenzoxazines (, ) with methyl iodide the hydrogen iodide formed in the S-methylation process brings about ring-opening and gives iodomethylthiolcarbamates (, ). Under similar conditions, the thioether salts (, ) of the structurally isomeric - and -2-thioxo-1,3-perhydrobenzoxazines, corresponding to the unstable intermediates in the former reactions, are stable. Under more vigorous conditions, the isomer thioether salt is transformed into the corresponding -and -l,3-perhydrobenzoxazin-2-ones (, ) by ring-opening and subsequent ring-closure, whereas the isomer gives only -1,3-perhydrobenzoxazin-2-one (). 相似文献
19.
Reactivity of pyridazines , , , towards ethoxycarbonylradical (generated by redox decomposition of oxyhydroperoxide of ethylpyruvate) was studied. Application of this type of homolytic substitution for synthesis of hitherto not accessible pyridazine carboxylic acid esters , , , , , , , is demonstrated. In addition improved synthesis of diethyl 4,5-pyridazinedicarboxylate () is proposed. 相似文献
20.
The - and -2-amino-4-cyclohexene-1-carboxylic acids and react with imidates to give the condensed-skeleton, bicyclic - and -pyrimidin-4-ones and . The amino acids and were reduced to the -and -1, 3-aminoalcohoIs and , which were cyclized by means of imidates to the bicyclic tetrahydro-4-3,1-benzoxazines and , or were converted, the corresponding carbamates and into the tetrahydro-4-3,1-benzoxazin-2(1)-ones and . The 2-thioxo analogues and were prepared by cyclization of the dithiocarbamates obtained from the aminoalcohols and by treatment with carbon disulphide. The -aminoalcohol and its saturated analogue reacted with -chlorobenzaldehyde to furnish the hexahydro and octahydro-4-3,1-benzoxazine , respectively. 1H and 13C NMR studies showed that, similarly to the earlier-investigated analogues containing oxygen or unsubstituted nitrogen at position 1, the synthesized isomrs , , and occurred as the preferred conformer in the heterocyclic twist inverse form of -inside type ( C6-N bond) (B). In the isomers containing a saturated C-2 atom ( and ), H-2 and H-6 are in relative positions. 相似文献