Maleic anhydride intermolecular

A domino reaction,in this case consisting of an inter- and an intramolecular Diels-Alder reaction, is a key step in the synthesis of the hydrocarbon pago-dane 30, reported by Prinzbach et al When the bis-diQnQ 27 is treated with maleic anhydride 4, an initial intermolecular reaction leads to the intermediate product 28, which cannot be isolated, but rather reacts intramolecularly to give the pagodane precursor 29 ... 

Dailey and colleagues109 employed a domino Diels-Alder reaction to synthesize the complex hexacycle 146. The intermolecular reaction of tetracycle 143 with maleic anhydride 144 afforded a single adduct (145) which immediately underwent an intramolecular Diels-Alder reaction to give 146 (equation 42). This reaction is similar to a reaction performed previously by Prinzbach and colleagues110. Prinzbach observed that when alkynes were used as dienophiles, either domino or pincer Diels-Alder reactions occurred. In the latter type, the triple bond reacts with both diene units. 

Intermolecular cycloadditions involving pyridinones are well known (80H(14)1793). 4-Cyano-l-methylpyridin-2-one undergoes Diels-Alder reaction with a suitable diene (equation 195) (79H(12)l). The pyridinone (307) forms 1 1 and 1 3 adducts on reaction with DMAD under pressure (Scheme 225) (82H(19)499). 2-Azabarrelenone (308) may be prepared by a sequence (Scheme 225), the first step of which is the addition of maleic anhydride to l-benzylpyridin-2-one (80AG(E)463). 

Drawn from these examples it is apparent that controlling the chemose-lectivity in inter-intermolecular Heck-Diels-Alder reactions of two different alkenes can be tedious if the alkenes show comparable reactivities. Nevertheless, the stepwise approach was realized in several other cases. In a synthesis of a derivative of cephalostatin 1 containing a central benzene instead of the pyrazine ring, Winterfeldt et al. linked two steroidal systems by a Heck coupling and subsequently performed high pressure Diels-Alder reactions of the conjugated diene with electron-deficient alkynes [34], Another example, reported by Hayashi et al., involves a selective Heck reaction of a bromoglu-cal with ethylene or acrylic acid derivatives followed by cycloadditions with maleic anhydride or N-phenylmaleimide [35]. 

Diphenylmethane does not undergo cycloaddition reactions on direct excitation in the presence of electron acceptors (Gilbert and Lane, 1981). Reaction only occurs when the radiation is absorbed into the intermolecular charge-transfer band. With maleic anhydride [2 + 2] cycloaddition to one of the phenyl rings of diphenylmethane occurs and then the cyclohexa-1,3-diene so created reacts thermally with a further mole of the anhydride. Benzonitrile forms a number of cycloaddition products (Cantrell, 1977), e.g. with 1,2-dimethylcyclohexene [130], [131] and [132] are formed (Scheme 29). Products... 

Dienamides (133) readily undergo intermolecular [4 + 2] cycloadditions, as exemplified by the highly emfo-selective reaction of (136) with maleic anhydride giving (137) (Scheme However, the main advantage of the simple diene preparation (131) — (133) is the facile introduction of an alkenic chain. 

Note that such cis-dienic structures can be present only if intermolecular oligomerization of nitrile groups has taken place.) The Diels-Alder product interrupts conjugation, thus reducing color formation. In the particular case of maleic anhydride, and under the relatively rough conditions of stabilization, this type of reaction should lead to crosslinking, by cross-anhydridization ... 

The reaction of dienophiles with polyacetylene (33) was investigated for limiting the decomposition of the polyene. Previously, intermolecular Diels-Alder reactions involving ds bonds were believed to form cross-links and render polyacetylene intractable, and that their elimination would lead to soluble products (34). No reaction of maleic anhydride or benzoquinone with polyacetylene was observed. In contrast, a second study (35) described the successful formation of the Diels-Alder adduct of maleic anhydride with remnant cis bonds in thermally isomerized samples of fran -polyacetylene. These data were used to support the notion that the thermal isomerization process used to convert cw-polyacetylene to the trans isomer does not go to completion. Unfortunately, the effect of this transformation on the tract-ability or stability of the polymer was not noted. 

A v/c-dihaloadamantane undergoes the intermolecular reductive dimerization via unstable adamantene species to give stereoisomeric products in 80-90% yields, as in Eq. (34) [240]. Cathodic reduction of or, or -dibromo-l,2-dialkylbenzenes in the presence of dienophiles (maleic anhydride, etc.) and hinderd dienophiles provides diels-Alder adducts stereoselectively [241,242]. In this reaction, the dienophiles play a duel role as mediators... 

Compared to the Diels-Alder reactions of 5-alkoxyoxazoles, relatively few examples exist for intermolecular cycloadditions of aminooxazoles and their derivatives. Since the initial studies of 5-aminooxazoles by Kondrat eva only four others have been reported. 2-Amino-4-methyloxazole 66a reacted with diethyl maleate at room temperature in ethanol to provide a 35% yield of 67 and 11% of 68 (Fig. 3.19). The acetamide derivative 66b reacted with maleic anhydride at 50°C in toluene to give only the decarboxylated 3-hydroxypyridine 69. 

Intermolecular cyclization reactions are also possible, e.g., in the cyclopolymerization of divinyl ether with maleic anhydride ... 

Yuan et al. [120] has reported the research on PLA/PBAT blend foam. Maleic anhydride is used to enhance compatibility between PLA and PBAT. The compatibilization mechanism of maleic anhydride (MAH) is that MAH enhances intermolecular force by forming hydrogen bond between grafted MAH and polymer backbone. Grafting MAH onto PLA and PBAT is performed by reactive extrusion, which can improve the interfacial adhesion between PBAT and PLA matrix. In order to increase the maleicing reaction activity, a free radical initiator, 2, 5-dimethyl-2, 5-di-(/er/-butylperoxy) hexane (LlOl), can be used. 

In 1939 Bacon and Farmer showed that the reaction between c/s-1,4-polyisoprene (natural rubber) and maleic anhydride was accelerated by benzoyl peroxide and they originally suggested that the anhydride linked across adjacent double bonds (intramolecular reaction) or across non-adjacent double bonds (usually intermolecular reaction). They also observed that when the concentration of rubber in the solvent used for the reaction exceeded a few per cent the product gelled and became insoluble. In subsequent work in which the model system cyclohexene-butyl maleate was studied Farmer (1942, 1943) revised his earlier suggestions and concluded that reaction was more likely to be at the ally lie (a-methylene) carbon. 

The intramolecular and intermolecular dehydration of carboxylic acids leads to the formation of ketenes and acid anhydrides, respectively. Methylketene is formed in a 65.5% yield by the dehydration of propionic acid over Bi203 Si02 at 973 K. Maleic anhydride is produced by the dehydration of maleic acid over alumina or metal phosphates at 503-513... 

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