共查询到20条相似文献,搜索用时 46 毫秒
1.
The first exclusive regioselective fragmentation of primary ozonides controlled by remote carbonyl groups on ozonolysis of norbornene derivatives and reaction of final ozonides with triethylamine as a new probe for determining the regiochemistry of carbonyl oxide formation from primary ozonide fragmentation are reported. Ozonolysis of the endo adducts 3a-d and the deuterated compounds 8a and 8b in CDCl(3) at -78 degrees C gave the final ozonides 4a-d, 9a, and 9b as the sole products (>95%), respectively. No detectable amount of the isomeric final ozonides 5, 10, 11, and 12 was obtained. A mechanism is proposed to account for the exclusive regioselective fragmentation of the primary ozonides. Ozonolysis of 3a-d, 8a, and 8b in CH(2)Cl(2) at -78 degrees C followed by treatment with triethylamine exclusively gave the convex tetraquinane oxa cage compounds 16a-d, 19a, and 19b in 85-90% yields, respectively. No detectable amount of the other regioisomers 17a-d, 20a, and 20b was obtained. Ozonolysis of 3a-d, 8a, and 8b in CH(2)Cl(2) at -78 degrees C followed by reduction with dimethyl sulfide gave the tetraacetal tetraoxa cage compounds 21a-d, 23a, and 23b in 85% yields, respectively. The difference in function between triethylamine and dimethyl sulfide in reaction with final ozonide is demonstrated. Ozonolysis of the endo adducts 24a and 24b in CDCl(3) at -78 degrees C exclusively gave the final ozonides 27a and 27b, respectively. The order of the preference of various remote carbonyl groups to control the fragmentation of the primary ozonides formed by ozonolysis of norbornene derivatives is investigated. Ozonolysis of the endo esters 32a-c in CH(2)Cl(2) at -78 degrees C followed by reduction with dimethyl sulfide gave the new tetraacetal oxa cages 35a-c, with an alkoxyl group directly on the skeleton, and the novel triacetal oxa cages 36b and 36c, respectively. The structures of triacetal oxa cages are proven for the first time by X-ray analysis of the crystalline compound 36c. 相似文献
2.
O. S. Kukovinets M. I. Kislitsyn R. A. Zainullin M. I. Abdullin F. Z. Galin 《Russian Journal of Organic Chemistry》2006,42(3):396-402
Ozonolysis of naphthalene in aqueous methanol, followed by the reduction of peroxy compounds thus formed with potassium iodide in the presence of acetic acid, gave 3-methoxy-2-benzofuran-1(3H)-one. In the absence of water, the product was methyl o-formylbenzoate. The latter was used as a synthon for the preparation of aromatic analogs of (2E)-2,6-dimethyloct-2-ene-1,8-diol ethers which are effective juvenoids. 相似文献
3.
Tandem radical cyclization-based strategy for the synthesis of oxa- and aza-cage compounds is described. The aryl iodides 1 and N-tosyl propargylated amine 8 lead to oxa- and aza-cages, respectively, after two tandem 5-exo-trig radical cyclizations. The alcohols 11 on reaction with nBu3SnH and AIBN give rise to the oxa-cages 14 bearing the tributyltin moiety after three tandem 5-exo-trig cyclizations. On the other hand, reaction of the propargyl ether 16 under similar conditions furnishes the oxa-cage 17 by a 5-exo-trig, 4-exo-trig, 5-exo-trig tandem radical cyclization sequence. 相似文献
4.
Ozonolysis of bis-endo-diacylbicyclo[2.2.1]heptenes 3a-d at −78 °C in dichloromethane-methanol gave the hydroperoxides 6a-d in 70-80% yields. Ozonolysis of bis-endo-diacetylbicyclo[2.2.2]octene 15 and bis-endo-diacetyl-7-oxabicyclo-[2.2.1]heptene 16 under the same reaction conditions gave the hydroperoxides 17 and 18, respectively. The intramolecular sequential nucleophilic addition of the carbonyl groups to the carbonyl oxide group was observed for the first time and was found to be faster than the intermolecular nucleophilic addition of a methanol molecule to the carbonyl oxide group. Ozonolysis of compound 23 in CH2Cl2-MeOH at −78 °C followed by reduction with Me2S gave compounds 24 and 25, in which the stereochemistry of the methoxyl groups was determined by X-ray analysis. 相似文献
5.
Hemant Kumar Srivastava Abed Al Aziz Quntar Abdulatif Azab Avital Shurki 《Tetrahedron》2009,65(22):4389-3774
The reaction of 6-chloro-1-hexynylphosphonate with primary and secondary amines afforded exclusively 2-aminocyclohexenylphosphonates in 62-85% isolated yields. In contrast, reaction of various amines with isobutyl 7-chlorohept-2-ynoate in acetonitrile at 70 °C gave (E)-sec-butyl 2-(1-alkylpiperidin-2-ylidene)acetates in 65-78% isolated yields. Calculations offer an explanation for the difference in the behavior of the two compounds classes. It is shown that C-C cyclization in the alkyne-phosphonate group occurs via an initial formation of a zwitterionic intermediate, which is stabilized by both an inductive effect of the phosphonate group and a newly formed hydrogen bond. The alkyne-carboxylate group, on the other hand, proceeds via enamine formation as a result of the smaller inductive effect of the carboxylate combined with involvement of an allene-like resonance form. This resonance form both delocalizes the negative charge in the zwitterionic intermediate making it to be less available for attack, and affects the geometry thus preventing formation of the stabilizing hydrogen bond. Hence, the zwitterionic intermediate of the alkyne-carboxylates is less stable leading to formation of an enamine, which is followed by N-C cyclization to give the azaheterocycles. 相似文献
6.
Promoted by triethylamine, α,β-unsaturated N-acylbenzotriazoles reacted with amino compounds in a variety of ways. Thus, N-cinnamoylbenzotriazoles reacting with aromatic amines afforded novel addition products β-benzotriazolyl amides 3, which might be normally formed from the alternative but unknown 1,4-addition of benzotriazole to N-cinnamoylamides. The type 3 compounds could also result from the reaction between N-crotonoylbenzotriazole and aliphatic amines. However, normal 1,4-addition could occur between α,β-unsaturated aliphatic N-acylbenzotriazoles and aromatic amines, leading to β-amino N-acylbenzotriazoles 4 in good yields. In addition, exclusive 1,2-addition of aliphatic amines to N-cinnamoylbenzotriazoles gave excellent yields of cinnamides 5. Accordingly, three possible routes were proposed to rationalize the formation of compounds 3-5. Finally, with o-phenylenediamine and o-aminothiophenol as the substrates, the 1,4- and 1,2-addition to α,β-unsaturated N-acylbenzotriazoles could take place concurrently and the corresponding heterocycles 1,5-benzodiazepine-2-one and 1,5-benzothiazepine-4-one were constructed, respectively. 相似文献
7.
Tetraacetal oxa-cage compounds 5a and 5b and convex oxa-cage compounds 7a and 8b are synthesized in a short sequence. Ozonolysis of endo adducts 2a and 2b in dichloromethane at ?78 °C followed by reduction with dimethylsulfide gave tetraacetal oxa-cages 5a and 5b in 35% yields respectively. Ozonolysis of 2a in dichloromethane at ?78 °C followed by treatment with triethylamine gave the convex oxa-cage 7a in 34% yield. These results support an acid-base proton transfer between the final ozonides and the base. The reasons that these oxa-cage compounds formed in low yields are discussed. The synthesis of tetraacetal oxa-cage 14, possessing aromatic substitutents directly on the skeleton of the oxa-cage, is accomplished. 相似文献
8.
Several novel tetraacetal oxa-cage compounds 9a-9f were synthesized from the corresponding 2-methylthiofurans la-lf by a short sequence. The structures of these tetraoxa-cage compounds were deduced from their spectral data and proven by X-ray analysis of 9a . Ozonolysis of the endo adducts 5a-5f in CH2C12 at ?78 °C followed by reduction with dimethyl sulfide gave the tetraoxa-cages 9a-9f in 65-75% yields, respectively. Ozonolysis of the exo adduct 6a under the same reaction conditions gave the tetracarbonyl compound 10 . The phenylthio group substituted tetraoxa-cage 13 and the tetraacetal oxa-cage 17, with one more carbon atom on the apex position, were also synthesized in a similar sequence. 相似文献
9.
An efficient, unusual Mannich type reaction of tertiary aromatic amines, formaldehyde and 1,3-dicarbonyl compounds is described in aqueous micelles catalyzed by boric acid to afford dialkylaminoarylated 1,3-dicarbonyls. In this unusual Mannich type reaction, tertiary aromatic amines react with formaldehyde to generate an N-alkyl-N-(4-methylenecyclohexa-2,5-dienylidene)alkylaminium intermediate (aza quinone methide), which undergoes nucleophilic addition with 1,3-dicarbonyl compounds. The reaction is highly regioselective, and exclusively para functionalized products are formed in high yields. 相似文献
10.
The synthesis of 4-oxo- and 4-anti-formyl-8,10,12,13-tetraoxapentacyclo[5.5.1.02,6.03,11.05,9]tridecanes has been accomplished. Ozonolysis of compounds 10a,b and 12a-c in dichloromethane at −78 °C followed by reduction with dimethyl sulfide gave the title compounds, 4-oxo-tetraoxa-cages 11a,b and 14a-c, in moderate yields. Ozonolysis of the endo-syn isomers 15a,b and 18a,b under the same reaction conditions gave 4-anti-formyl-tetraoxa-cages 17a,b and 20a,b, respectively. 相似文献
11.
A diastereoselective concise synthesis of the iminosugars DMDP and DAB is presented starting from l-xylose and affording the two alkaloids in good yields of 35% and 22% over seven and eight steps, respectively. The Petasis borono–Mannich reaction of 3,5-di-O-benzyl-l-xylofuranose with benzylamine and (E)-styrylboronic acid served as the nitrogen-introducing key step furnishing the new C–N bond in an entirely diastereoselective manner. A chemo- and regioselective O-mesylation followed by an intramolecular SN2-cyclisation allowed the formation of the pyrrolidine ring. Ozonolysis of the styryl double bond and subsequent reduction to form the C-5 hydroxymethyl substituent followed by hydrogenolysis of the benzyl protecting groups concluded the DMDP synthesis. Furthermore, an unexpected fragmentation process during the ozonolysis reaction also gave access to the C-5 decarbinolated DMDP derivative DAB. 相似文献
12.
The solid-phase library synthesis of trisubstituted guanidines was accomplished. Amines were loaded onto the 4-formyl-3,5-dimethoxyphenoxymethyl linker via reductive amination. Subsequent acylation with Fmoc-4-aminomethylbenzoic acid followed by Fmoc deprotection gave solid-supported primary amines. Alternatively, sulfonylation of resin-bound secondary amines with 4-cyanobenzenesulfonyl chloride followed by borane reduction also gave solid-supported primary amines. Both resins were acylated with isocyanates to furnish solid-supported ureas. Dehydration of ureas with p-toluenesulfonyl chloride in pyridine gave solid-supported carbodiimides. Nucleophilic addition of amines to the carbodiimide bond followed by cleavage off the solid support gave trisubstituted guanidines. 相似文献
13.
Several novel triacetal trioxa-cage compounds 11a-11g, 13, 15, 17 and 19 are synthesized in a short sequence. Ozonolysis of bicyclo[2.2.1]heptenes 4a-4c, 8a-8c, 10a, 10b and 14 in dichloromethane at ?78 °C followed by reduction with dimethyl sulfide gave triacetal oxa-cages 11a-11g, 13 and 15 in moderate yields, respectively. Ozonolysis of bicyclo[2.2.2]octenes 16 and 18 under the same reaction conditions gave triacetal oxa-cages 17 and 19 in moderate yields, respectively. 相似文献
14.
Iodoethynylbenzene as iodoalkyne model compound was aminocarbonylated with tert-butylamine under carbon monoxide atmosphere in the presence of in situ palladium(0) catalysts. The formation of the unsaturated carboxamide (alkynyl amide) is always accompanied by that of the Glaser coupling product, diphenylbutadiyne. The yield of the amide-forming reaction was optimised by the systematic variation of the phosphine ligand, carbon monoxide pressure and temperature. The scope of the reaction was investigated by using various primary and secondary amines including amino acid methyl esters as N-nucleophiles.17α-(Iodoethynyl)-testosterone was also functionalised by using this methodology providing the corresponding 17α-(carboxamidoethynyl)-testosterone derivatives in up to 96% yields. The reaction was extended to 1-(iodoethynyl)cyclohex-1-ene and 1-iodohex-1-yne. Ethyl iodopropiolate gave the enamine type product by the addition of amine to the alkyne functionality which was formed from the iodoalkyne via deiodination under standard aminocarbonylation conditions. The bromo analogue, bromoethynylbenzene has shown lower reactivity than the corresponding iodo derivative. 相似文献
15.
Martín Soto Raquel G. Soengas Artur M.S. Silva Vicente Gotor-Fernández Humberto Rodríguez-Solla 《Tetrahedron》2018,74(38):5475-5480
A general and highly selective method for the synthesis of carbohydrate-derived (Z)-vinyl halides and silanes is described. This reaction takes place through a β-elimination process of sugar-derived α-halomethylcarbinol acetates promoted by samarium diiodide. Starting materials have been easily prepared in two steps consisting in an initial addition of halomethyllithium compounds to the corresponding galactose-derived aldehyde, followed by acetylation. A mechanism that explains both the formation of (Z)-vinyl derivatives and its selectivity is proposed. Finally, the synthetic usefulness of these compounds has been applied in cross-coupling reactions with ethynyl benzene towards the formation of selected enyne derivatives. 相似文献
16.
Allylic substitution of secondary γ,γ-disubstituted allylic picolinates with ArMgBr-based copper reagents was applied to the synthesis of LY426965. Reduction of (R)-6-(PMB-oxy)-3-hexyn-2-ol of 93% ee (PMB?=?p-MeOC6H4CH2) using Red-Al gave (R,Z)-4-iodo-5-(PMB-oxy)hex-3-en-2-ol, which was later converted to the Me-substituted allylic picolinate by Pd-catalyzed coupling with MeZnI followed by esterification with picolinic acid. Allylic substitution with PhMgBr/Cu(acac)2 proceeded with high anti SN2′ selectivity (99%). Ozonolysis, addition of c-Hex-MgBr to the resulting aldehyde, and reductive amination with the piperazine derivative afforded LY426965. 相似文献
17.
Xi-Cun Wang Guo-Jun Yang Xiao-Dong Jia Zhang Zhang Yu-Xia Da Zheng-Jun Quan 《Tetrahedron》2011,67(18):3267-3272
The Biginelli 3,4-dihydropyrimidin-2(1H)-one was converted to various C2-multifunctionalized pyrimidines via the dehydrogenation and Mitsunobu reaction using amines, alcohols, phenols and carboxylic acids as nucleophiles. A possible mechanism was also proposed to rationalize the formation of products. 相似文献
18.
Djamel Chergui Mamar Hamdi Michel Baboulne Vincent Spziale Armand Lattes 《Journal of heterocyclic chemistry》1986,23(6):1721-1724
The reaction of primary amines (methylamine, isopropylamine, benzylamine) in neutral medium, on 3-cinnamoyl-2-pyrones gave 7-amino-3,5-dioxo-l,6-octadienes 2 . The formation of these compounds is presumed to occur via nucleophilic attack of amines with a ring opening reaction followed by decarboxylation. Their structures were determined unambiguously by 1H, 13C nmr spectroscopy, elemental analysis and mass spectrometry. 相似文献
19.
The rearrangements of 4′-methoxy-N-methyl- and N-methyl-4′-nitro-diatzoaminobenzene have been studied in 20% acetonitrile/aqueous buffers. The reactions are specifically acid catalyzed and involve pre-equilibrium formation of amine and diazonium salt followed by rate-limiting attack of the diazonium ion at a C-atom (C-coupling) to give the corresponding aminoazo compounds. There is no evidence to suggest that, under the present conditions, mechanisms other than the established Friswell-Green mechanism occur. The traditional two-stage synthesis of aminoazo compounds via isolated diazoamino compounds can therefore be replaced by a one stage process for amines which undergo initial attack at a N-atom by diazonium ion (N-coupling). 相似文献
20.
The study of the chemical modifications of model compounds of the diglycidyl ether of bisphenol A/triethylene tetramine (DGEBA/TETA) epoxy resins under electron irradiation is described. The reaction of butylamine and N,N′-diethylethylene diamine with DGEBA afforded model compounds of the DGEBA/TETA structure. Nanometric silica was used as filler for these model compounds. 1H and 13C NMR analyses allowed identification of the chemical structures before and after irradiation. C-O and C-N scissions were observed with the formation of phenolic and methyl-ketone ends and of primary and secondary amines. For the model compounds containing the 1,2-diaminoethylene structure, the scission of the C-N bond is followed by the formation of an enamine end. The mechanisms of the different bond scissions are proposed. The presence of the nanometric silica fillers allows the protection of some C-N bonds. The reaction of the chemical species formed by electron irradiation with the reactive functions at the silica surface is proposed to explain the chemical modifications observed on the irradiated filled model compounds. 相似文献