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1.
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
2.
Wojciech Dmowski 《Journal of fluorine chemistry》1984,26(3):379-394
1-Phenylpentafluoropropenes readily react with lithium dialkylamides to give, in most cases, mixtures of 1-aminosubstituted alkenes and 2-amino-substituted alkenes , with the latter being the favoured products. The reactions with bulky lithium diethylamide and lithium 2-methylpiperidinoamide gave exclusively 1-amino-substituted products . The effect of the increased bulk of N-nucleophiles is opposite to that observed for the reactions of alkenes with C-nucleophiles Increasing electronegativity of the phenyl ring substituents in alkenes shifts the regioselectivity of the attack of lithium amides towards the C2 carbon atom. The E to Z isomer ratios of enamines were found to be time dependent and the slow isomerisation of the kinetic isomers E to the thermodynamic isomers Z was observed, while the ratio of isomers of enamines did not change with time.A concerted, single-step process is suggested for the reactions of alkenes with lithium dialkylamides, and a tentative explanation of the different stereochemistry of enamines and is given. 相似文献
3.
《Tetrahedron》1986,42(20):5739-5746
Substrates such as () undergo regiospecific attack by azide and thiocyanate ions at the terminus of the CC-CN-CO system. In the case of addition of azide, this is proved by the detailed analysis of the 1H and 13C NMR spectra of the products () derived from the quinone-imides (). The structure of the products obtained by the addition of thiocyanate to the quinone-imides and ()() is proved by their facile cyclisation to the 2-aminobenzothiazoles () and () respectively. 相似文献
4.
From aldehydes, ketones and esters β-carbonyl radicals can be generated via enolization, cyclopropanation, solvomercuration and reduction with NaBH4. Radicals react with electron-poor alkenes to give products of CC-bond forming reactions (Tables 1–3). Carbonyl compounds are therefore precursors of three-carbon building blocks. The products result from reactions with “Umpolung”. 相似文献
5.
Irradiation of in methanoi with λ 254 nm yields and as the main primary products which result from the excited singlet state hy initial cyclopropane bond homolysis, but no primary photosolvolysis products. 相似文献
6.
α,β-epoxy-artemisia ketone, undergoes intramolecular cyclisation by OM-DM yielding the tetrahydrofuran derivatives – , while on treatment with BF3,-etherate cyclises to the cyclopentanones and . The structure of all products has been elucidated by spectral methods. The mechanism of the cyclisation reaction is discussed briefly. 相似文献
7.
In an attempt to prepare short-bridged hydroxymetacyclophanes , the spirocyclohexadienones were pyrolyzed by flash vacuum thermolysis (FVT). Instead of , variable amounts of 4-(5-hexenyl)phenol (), β-hydroxybenzocycloalkenes () and 4-(trans-1-alkenyl) phenols () were obtained. The formation of these products is explained by invoking cleavage of a spiro bond in under formation of the intermediate diradical which, depending on the length of the aliphatic chain and on the temperature, has several pathways open for isomerization to spin-paired products. 相似文献
8.
Wojciech Dmowski 《Journal of fluorine chemistry》1980,15(4):299-313
Unlike unsubstituted perfluoropropene [1,2] 1-(2-tetrahydrofuryl)-pentafluoropropene reacts with sodium alkoxides in parent alcohol solutions to give 1-alkoxy-1-(2-tetrahydrofuryl)-tetrafluoropropenes as major products and 1-alkoxy-2H-1-(2-tetrahydrofuryl)-pentafluoropropanes as very minor products. The yield of adducts is, to some extent, increased by the reduced basicity of the alkoxide ion. Results are discussed in terms of the supposed properties of the carbanionic intermediates involved.N.m.r., m.s., and i.r. data for, and some chemical properties of compounds , viz., further reactions with sodium alkoxides and hydrolysis are described. 相似文献
9.
The reactions of dimetalated succinamides with a variety of electrophiles give 2,3-disubstituted adducts ( with high diasterioselectivity and annelated products (–). 相似文献
10.
The cyclic thiocarbonates to react with tri(n-butyl)tin hydride under formation of the deoxygenation products , , , and . The unexpected regioselectivity of this reaction with the compounds and will be discussed in the following. 相似文献
11.
The synthesis of diketones , and starting from diene by photochemical cyclization followed by RuO4 oxidation is described and stereochemistry of products is proposed. 相似文献
12.
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
13.
trans- -Isopropenyl-4-methylene-spiro[2.x]alkanes ( and ) react at 0°C with CSI to give as major products the trans bicyclic cycloazanondienones (-) and as the minor products bicyclodihydro-azepinones ( and ), and the respective cis isomer of bicyclic cycloazanondienones ( and ). 相似文献
14.
Reduction of the indole-1-carboxaldehydes (-) with borane /THF gives the 1-methylindoles () in 42-91-% yields together with the di(indolylmethyl)ethers (), the indolyl-methyl indolines (), the unsymmetric ether() and the indolenine () as the minor products, except . This appears to be the first report on the formation of symmetric ethers in the borane/THF reduction of an oxygen function. The formation of and from and implies that electrophilic substitution takes place primarily at position 3 of 3-substituted indoles, did not form the corresponding probably because of steric hindrance. These results are discussed in relation to the mechanisms of borane/THF reduction, origin of the different products and electrophilic substitution in 3-substituted indoles. 相似文献
15.
4-Trimethysilyl-3-dialkylaminocrotonate esters () react with a number of carbonyl electrophiles and titanium tetrachloride to give products with substitution at γ-position. A dynamic equilibrium of and its O-silyl isomer is proposed to explain the regiochemistry. 相似文献
16.
Wojciech Dmowski 《Journal of fluorine chemistry》1984,26(2):223-241
Reactions of 1-phenylpentafluoropropenes – with a number of alkyllithium reagents were investigated in detail. In all cases mixtures of 1-alkly-1-phenyltetrafluoropropenes and 2-alkyl-1-phenyltetrafluoropropenes were obtained. The ratio of products and is strongly influenced by both the electronegativity of the benzene ring substituents and the bulk of the alkyl group of the alkyllithium reagents. The increase of both of these factors favours formation of 2-alkyl-substituted alkenes with a reduced yield of 1-alkyl-substituted alkenes . The influence of the benzene ring substituents in alkenes obeys the Hammett type correlation, while the influence of the bulk of the alkyllithium reagents exhibits good relationships with the Fellous and Luft scale of steric substituent constants Exs ; no linear correlation with other scales of steric constants was found. Overall regioselectivity, in the reaction of 1-phenylpentafluoropropenes with alkyllithium reagents, considering both the influence of the benzene ring substituents and steric factors, is expressed by the Pavelich-Taft type equation. Observed direction of the influence of the bulk of the alkyllithium reagents on the ratio of products and is interpreted in terms of steric strains influencing the geometry and free energy of the supposed intermediates involved in these reactions. 相似文献
17.
Nb-oxides and in the presence of acetic anhydride led to products , or with participation of the indole nucleus during the fragmentation reaction. 相似文献
18.
Oxidation of benzotropylium () fluoborate with Na2O2 and KO2 gives the benzotropones, and , as the major products with no naphthalene () or other ring contracted products formed. Oxidation with -chloroperoxybenzoic acid produces a small amount of naphthaldehydes ( and ) and even less naphthalene, a long with the benzotropones, while oxidation with H2O2 and -butyl peroxyacetate gives slightly more of the ring contracted naphthaldehydes than benzotropones, in addition to a small quantity of naphthalene. All reactions produce some 1,2-benzotropilidene () 相似文献
19.
《Tetrahedron》1986,42(21):5841-5848
The preparations and silver-assisted acetolyses of the 1-methoxy (), 1-methyl (), 1-carbomethoxy (), and 1-nitro () derivatives of -7,8-dichlorodibenzobicyclo [2.2.2] octa-2,5-dienes are described. Rearranged products possessing the dibenzobicyclo [3.2.1] octadiene skeleton were identified. With compound , the P8:P7 ratio (ratio of products derived from ionizations of C8-Cl and C7-C1 bonds) was 1.3. For and , the corresponding P8 P7 ratios were 0.4 and 33 respectively. Acetolysis of led to products in detectable quantities from ionization of the C8-C1 bond only. The data support the proposal by Cristol that the transition states for these solvolytic rearrangements more closely resemble phenonium ion-like intermediates than benzyl cations. 相似文献
20.
The chiral bicyclic lactam () derived from levulinic acid and (S)-valinol is sequentially alkylated and then cleaved to 2,2-dialkyl levulinaldehyde () which is cyclized to the title products () in > 99% ee. 相似文献