Maleimide Diels-Alder reaction with

Maleimides have three principal reaction pathways. These are radical addition to vinyl compounds the Michael addition with compounds having active hydrogens and the Diels-Alder reaction with dienes (Fig. 3). Any of the three can be tools for forming thermosetting adhesives. 

Various o-quinodimethanes, generated in situ from o-alkenylbenzyltributyl-stannane precursors, have been used to synthesize functionalized polycycles by Diels Alder reaction with maleic anhydride, methylacrylate, dimethylfumarate and N-phenyl maleimide in the presence of electrophiles [37] (Scheme 2.16). 

Coordination of Ni(0) to the alkyne gives a n complex, which can be written in its Ni(II) resonance form. Coordination and insertion of another alkyne forms the new C6-C7 bond and gives a nickelacyclopenta-diene. Maleimide may react with the metallacycle by coordination, insertion, and reductive elimination to give a cyclohexadiene. Alternatively, [4+2] cycloaddition to the metallacycle followed by retro [4+1] cycloaddtion to expel Ni(0) gives the same cyclohexadiene. The cyclohexadiene can undergo Diels-Alder reaction with another equivalent of maleimide to give the observed product. 

Discussion. The combination of BCB with BMI significantly improves the properties of the BMI, apparently by tying up the maleimide in a Diels-Alder reaction with the transient diene formed from the opening of the cyclobutene ring. Both the thermal and the thermomechanical properties are improved almost to the level of the BCB... 

The reaction of the bisbenzocyclobutene 41 with the bismaleimide 44 is similar to the reaction of 41 with the activated diacetylene 43. From the DSC thermogram in Fig. 24 it is apparent that there is one major exotherm peak at 258.8 °C associated with this reaction. This could be interpreted as either being the polymerization exotherm peak for a benzocyclobutene-maleimide Diels-Alder reaction or else it is the coincidental overlap of the exotherm peaks associated with each pure component. This latter case is a distinct possibility since both the pure bisbenzocyclobutene 41 and the pure bismaleimide 44 have... 

A.2.5. Asymmetric Diels-Alder Reactions with Maleimides... 

The maleimide C=C double bond can undergo a Diels-Alder reaction with dienes for example, reaction with o,o -diallylphenols is thought to proceed initially by ene-synthesis, followed by Diels-Alder reaction ... 

The Diels-Alder reaction with /V-phenylmaleimidc has frequently been used for the separation, purification, and structure determination of ortho photocycloadducts [12,47,86,90,108,116,126,132,133,138], Other dienophiles that have been successfully employed in Diels-Alder reactions with ortho adducts are A-(para-bromophenyl)maleimide [116,120], maleimide [116,118,127], maleic anhydride [127,191], tetracyanoethylene [11], and dimethyl acetylenedicarboxy-late [73,127], The Diels-Alder product of A-(para-bromophenyl)maleimide with the exo-ortho adduct formed from 1,4-dioxene and benzene [120] and the Diels-Alder product of maleimide with the endo-ortho adduct from cis-cy-clooctene and benzene [118] were obtained in crystalline form and their structures could be determined by means of x-ray diffraction. 

Such syntheses take advantage of transannular intramolecular hetero Diels-Alder reactions [426], another impressive example is the diene transmissive hetero Diels-Alder reaction of the thioketone 5-14. The diene 5-15 formed by this cycloaddition underwent a second Diels-Alder reaction with N-phenyl-maleimide to yield the fused polycycle 5-16 as single diastereomer (Fig. 5-5) [427]. 

Vinylimidazoles participate in Diels-Alder reactions with a wide variety of dienophiles <2006SL965>. Thus, cycloadduct 508 is obtained at room temperature on reaction of compound 506 with A -phenylmaleimide 507 in 91% yield. A similar reaction occurs between natural product oroidin 509 and maleimide 510 to give cycloadduct 512 with catalysis by Y(OTf)3 511 (Scheme 116) <20060L819>. 

The Diels-Alder reaction of 3,6-dimethoxybenzocyclobutene 30 with some dienophiles was studied (Scheme 9). A mixture of benzocyclobutene 30, A -phenyl-maleimide 54, and benzene was heated at 210 in a sealed tube. The adduct 55 was obtained in 53% yield. The reaction of 30 and cyclohexenone 56 similarly gave the adduct 57 in 36% yield. In the case of dienone 58, however, the desired product could not be obtained. On the other hand, the Diels-Alder reaction with tranj-enone 59 afforded adduct 60 in a good yield (76% yield). Therefore, we felt confident that the reaction of benzocyclobutene 30 with enone (+)-31 would give the desired adduct with a tetracyclic skeleton. 

Diels-Alder reaction with support-bound 4-[3-(tert-butyldimethylsilyloocy)buta-l,3-die-nyl] groups (Scheme 65) [310] N-[(Fluoren-9-ylmethoxycarbonyl)ethyl]maleimide (304) (135 mg, 0.375 mmol) was weighed into a screw-cap vial (Reacti-Vial) and toluene (800 pL) was added. The vial was sealed and heated until the dienophile dissolved, and resin bearing a diene (302 or 306) was added and allowed to swell in reagent and solution. The vial was sealed and kept at 110 °C overnight The reaction solution was drained and the resin washed as follows ... 

Similar to the 2-vinylindole species, the 3-vinylindole derivatives have also been extensively used in synthesis, due to their ability to take part as the 47t component in Diels-Alder reactions with various dienophiles. WhUe some of the work in this field has involved structurally simple 3-vinylindole species, bicyclic structures such as biindoles, indole-quinones, and indole-maleimides have also been used as the 47t components. 

In reactions of the chiral 3-tosyl-2//-pyran-2-one A with ketene acetals (7) moderate selectivities were observed. 2-Substituted 1,3-butadienes with a chiral sulfoxide group have been studied in asymmetric Diels-Alder reactions with maleimide. These reactions have been found to proceed smoothly and highly stereoselective at 25°C. 

Sol 1. (i) Didehydro-Diels—Alder (DHDA) reaction of 1,2-di(cyclohex-1 -en-1 -yl) ethyne and A-methylmaleimide gives a cyclic aUene intermediate that further undergoes second Diels—Alder reaction with another molecule of A-methyl-maleimide to give the observed product. 

Polymers with pendent furfuryl residues readily undergo Diels-Alder reaction with MA and maleimides. " The polymers are potentially useful in ion-exchange resins and thermoset coatings. The poly(furfuryl methacrylate) or furfuryl methacrylate copolymers may be treated with MA to obtain a Diels-Alder product shown as follows ... 

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