Maleic anhydride unsymmetrical

Ohwada extends his theory, unsymmetrization of n orbitals, to Orbital Phase Environment including the secondary orbital interaction (Chapter Orbital Phase Environments and Stereoselectivities by Ohwada in this volume). The reactions between the cyclopentadienes bearing spiro conjugation with benzofluorene systems with maleic anhydride exemplified the importance of the phase environment. The reactions proceed avoiding the out-of-phase interaction between dienophile LUMO and the HOMO at the aromatic rings. The diene 34 with benzo[b]fluorene favored syn addition with respect to the naphtalene ring, whereas the diene 35 with benzo[c]fluorene showed the reverse anti preference (Scheme 22) [28]. 

Ethoxy)-allylidenecyclopropane (136a) readily underwent Diels-Alder reaction with activated dienophiles under mild conditions (Table 14) [33]. Only one regioisomer was formed with unsymmetrically substituted dienophiles such as methyl maleic anhydride (137), and quinones 138-141 (entries 2 and 3-6). AH the cycloadducts 143-147 derive from an endo approach between the two reagents. Two site-isomers were obtained in 96 4 ratio with 3-isopropyl-6-methyl-p-quinone (141) (entry 6) and the high site-selectivity observed in this... 

Cycloadducts have been successively obtained by reaction of MCP with maleic anhydride (116) and a number of related electron-deficient alkenes (137,486,487) under photolytic conditions in the presence of a sensitizer (Table 38, entries 5-8) [132b]. Analogous cycloadditions in mild conditions with high yields have also been performed with electron-donor substituted alkenes, such as vinylene carbonates 483 and 484 and the imidazolinone 485 (entries 2-4) [132], In the case of the unsymmetrical anhydride 137 (entry 6), an almost equimolar mixture of both the possible regioisomers has been obtained [132b]. In all these cases the reaction has also been proposed to occur via diradical intermediates formed from the reaction of 1 with the alkene in its excited triplet state [132]. 

The syntheses of photochromes in which the heterocycles are separated by the maleimide ring described in the literature were as time-consuming as the syntheses of compounds based on maleic anhydride. A general approach to these photochromes is exemplified in Scheme 55 using unsymmetrical photochrome 180 (98BCJ1101). Here, the treatment of 2-methoxybenzothiophene with oxalyl chloride and aminoacetonitrile... 

Unsymmetrical dipolarophiles led to the formation a single regioisomeric product acrylonitrile delivered adduct 19 exclusively while maleic anhydride... 

Diels-Alder Reaction. By means of the Diels-Alder reaction a considerable number of hydrobiphenyls have been prepared,486 from which it should be possible to obtain unsymmetrical biaryls by dehydrogenation. Only a few of the adducts have been converted to the completely aromatic compounds. o-Terphenyl has been prepared from the adduct of maleic anhydride and 3,4-diphenylcyclopentadienone,436 and p-terphenyl has been obtained in practically quantitative yield from the adduct of the methyl ester of acetylenedicarboxylic acid and 1,4-diphenylbutadiene.43d... 

Maleic anhydride is used in the manufacture of unsaturated polyester resins, copolymers, food additives, agricultural chemicals, and lube oil additives. Agricultural chemicals made from maleic anhydride include daminozide (Alar ), a growth regulator for apples that in 1989 was found to be carcinogenic because of a breakdown product, unsymmetrical dimethyl-hydrazine (UDMH). 

Cross-coupling of two unsymmetrical allylic complexes is possible by this transmetal-lation. particularly in the presence of maleic anhydride. 

Sridharan V, Karthikeyan K, Muthusubramanian S (2006) Unexpected multi-component reaction of 2/4-methoxyaryl aldehydes with aryUiydroxylamines and maleic anhydride a novel synthesis of unsymmetrical diarylamines. Tetrahedron Lett 47 4221 223... 

The diphosphetene-complex (154) undergoes a reversible, conrotatory ring-opening on treatment with maleic anhydride or N-phenylmaleimide, to form the complexed diphosphadiene (155). The reactions of P-halofunctional phospha-alkenes with N-trimethyl-silylimines and related compounds have given a series of azaphosphadienes (156). The first unsymmetrical 1,3-diphospha-... 

Na2[Fe(CO)4] is also used as a reductant, especially for the preparation of unsymmetric aldehydes or ketones. Reduction of maleic anhydride by Na2pe(CO)4 gives maleinalde-hydic acid (eq (10)) [40]. 

Unsymmetrical Anhydrides. Unsymmetrically substituted phthalic and maleic anhydrides show some curious selectivities. The selectivity for attack at one carbonyl group rather than the other is large enough to be useful to synthetic chemists, and it demands some kind of explanation. 

For example, heptatriene 6.290 and 1-cyanobutadiene 6.294 react with maleic anhydride and isoprene 6.293 to give mainly the lower-energy adducts 6.291 and 6.295, respectively, rather than the alternatives 6.292 and 6.296.837 These reactions are similarly governed both by the formation of the thermodynamically favoured products and by the initial overlap with the larger frontier orbital coefficient in each component leading to the unsymmetrical transition structure. 

The selectivities demonstrated by unsymmetrical maleic and phthalic anhydrides for attack of a nucleophile on one carbonyl group rather than on the other are large enough to demand explanation. In principle, maleic anhydride 126 can undergo attack by a nucleophile at either of the two carbonyl carbons Ca and Cp. However, there is exclusive attack at C by lithium aluminum hydride when R is a methoxy group. The ratio of attack at C versus Cp reduces only slightly to 88 12 when R is a... 

Later, Lewis acids were suggested as catalysts for Diels-Alder addi-tions in the case of the reaction of anthracene with maleic anhydride the acceleration due to AICI3 was estimated to be of the order of 10 . As has been mentioned (Section 4.1.1), in the presence of Lewis acids endo adducts are more favoured than in uncatalysed reactions, and there is more selectivity in orientation when unsymmetrical dienes and dienophiles add to each other furthermore, with an optically active reactant, asymmetric induction can be stronger in the catalysed reaction (Table 4, footnote b). it should be appreciated that substrates sensitive to AICI3 and similar catalysts are always polar molecules, usually containing carboxyl or carbonyl groups, to which Lewis acids can become bound. 

In most cases, the thermal ene reaction is thought to proceed by a concerted mechanism with a cyclic transition state, although this may be unsymmetrical, with one of the new ct bonds more highly developed than the other. The ene reaction often leads to predominantly the endo adduct (in which there is greater overlap of the two components). Thus, different major diastereomers are formed in the reaction of maleic anhydride with fi-2-butene and Z-2-butene, both of which arise from a preference for the endo transition state. Further evidence for the concerted nature of the reaction comes from the observation that the new C—C and C—H bonds are formed cis to each other. The cis addition is exemplified in the reaction of 1-heptene with dimethyl acetylenedicarboxylate to give the adduct 237 (3.152). In this reaction the adduct is formed with the two ester groups on the same side of the alkene such that the hydrogen atom and the allyl residue add to the same side of the triple bond of the enophile. 

Diels-Alder additions of 5-substituted cyclohexa-2,4-dienones have been explored. When the 5-substituent is methyl or methoxy, no self-dimerization takes place but the steric effects are such as to hinder weak dienophiles and even fully substituted strong dienophiles from forming adducts. Thus maleic anhydride and 2,3-dimethylbenzoquinone, but not dichloromaleic anhydride or tetracyanoethylene, formed adducts. The experimentally found orientations were consistent with a highly unsymmetrical biradical-like transition state rather than a fully concerted reaction. 

Begley, M. J., D. W. Knight, and G. Pattenden Regioselective Nucleophilic Additions to Unsymmetrically Substituted Maleic Anhydrides. Tetrahedron Letters 4279 (1975). and unpublished work. 

In this decarbonylative cycloaddition process, Ni(0) is thought to be responsible for CO elimination. Unsymmetrical substrates mostly lead to mixtures of regioisomeric isocoumarins terminal alkynes do not react due to their rapid Ni-induced oligomerization. Derivatives of maleic anhydride give rise to 2-pyrones. 

In the case of unsymmetrically substituted [4]radialenes, the four diene sites are no longer equivalent, and competing DA pathways become possible. The only study using a differentially substituted [4]radialene was published by Szeimies et al. in 1992 [61]. Tricyclic [4]radialene 184 was reacted with maleic anhydride, NPhM, benzyne, dimethyl acetylenedicarboxylate, TCNE, and 4-phenyl-1,2,4-triazole-3,5-dione. The only observed products resulted from reaction at the less sterically encumbered diene site, as illustrated by the representative example in Scheme 12.40 in which ewiio-adduct 185 and aco-adduct 186 were isolated in a combined yield of 57%. 

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