Diels-Alder reactions of maleimide

Several highly enantioselective Diels-Alder reactions are known for which the di-enophile does not fit any of the above classes. Corey and coworkers applied the chiral aluminum reagent 36 with a C2-symmetric stilbenediamine moiety (videsu-pra) to the Diels-Alder reaction of maleimides as dienophiles [54] (Scheme 1.68). In most asymmetric Diels-Alder reactions the reactants are usually relatively simple dienes such as cyclopentadiene or monosubstituted butadienes, and unsym-... 

The Diels-Alder reaction of maleimide (+)-45 with cyclopentadiene requires a prolonged reaction time (3 days) at room temperature in the absence of activating agents. The yield is around 80%. However, in the presence of Et2AlCl, the reaction can be completed with a quantitative yield within 20 minutes at room temperature (Scheme 5-11). 

Several research groups studied the asymmetric Diels-Alder reaction of maleimides, and applied those methods to natural product synthesis. 

Figure 8.19 Diels-Alder reactions of maleimide (23) and triphenylene (27) or perylene (8) within cage 2.

PEO-PSt-PtBA arms, PEO-fi-PSt, and PEO-b-PMMA was synthesized via Diels-Alder reaction of maleimide and anthracene end-functionalized polymers using ATRP or NMP. Durmaz et elegantly combined 1,3-dipolar cycloaddition with... 

Problem 12.10 Discuss how the following block copolymers can be prepared via Diels-Alder reaction of maleimide- and anthracene-end functionalized polymers (a) PMMA-fc-PSt, (b) PEG-fc-PSt, (c) PrBA-i>-PSt, and (d) PMMA-ii-PEG block copolymers. 

Figure 22 Diels-Alder reaction of maleimide 28 with furan 26 gives rise to two diastereoisomeric products, exo- and endo-30, which are both capable of accelerating their own formation in an autocatalytic manner. The two cycloadducts do not have any measurable catalytic effect on the formation of their partner diastereoisomer. Maleimide 27 was used as a control compound to give products exo-and endo-29 that highlight the importance of hydrogen bonding since the iV-methyl anihde is incapable of binding the carboxylic acid recognition site in 26.

Durmaz, H., Colakoglu, B., Tunca, U., and Hizal, G. (2(X)6a) Preparation of block copolymers via Diels-Alder reaction of maleimide- and anthracene-end functional polymers. Journal cf Polymer Science Part A-Polymer Chemistry, 44,1667. 

Modified diazaaluminolidine (116f) efficiently catalyzed asymmetric Diels-Alder reaction of maleimide (Scheme 6.146) [174]. Especially, the reaction of N-ortho-methylphenyl maleimide realized excellent enantioselectivity. In the first total... 

BMI also reacts with dienes to form Diels-Alder adducts [12]. When BMI reacts with a a,(n-biscyclopentadienyl compound or other bis-diene resin, the bis-maleimide chain is extended by the Diels-Alder reaction. Bis-maleimide, chain extended with bis-diene, is not used in adhesives. However, as the Diels-Alder reaction is reversible, there may be a possibility of recyclability of the cured resin by depolymerization of the backbone (Fig. 6). 

Engberts [3e, 9] has extensively investigated the Diels Alder reaction in aqueous medium. Recently Engberts and colleagues reported [9c] a kinetic study of a Diels Alder reaction of N-alkyl maleimides with cyclopentadiene, 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene in different solvents. The reaction rates of the cycloadditions with the open-chain diene relative to w-hexane are reported in Table 6.3. The aqueous medium greatly accelerates the Diels Alder reaction and the acceleration increases as the hydrophobic character of the alkyl group of the dienophile increases. These and other kinetic data [3e, 9], along with the observation that the intramolecular Diels-Alder reaction is also accelerated in... 

Mataka and coworkers reported the studies of the Diels-Alder reactions of [3.3] orthoanthracenophanes 96 and 97, of which anthraceno unit, the potential diene, has two nonequivalent faces, inside and outside. The reactions of 96 with dien-ophiles gave the mixtures of inside and outside adducts with the ratios between 1 1 and 1 1.5. However, the ratio changes drastically, in favor of the inside adducts, when 97 reacts with dienophiles such as maleic anhydride, maleimide and naphto-quinone [55] (Scheme 46). Mataka suggested that the Jt-facial selectivity is controlled by an orbital interaction between the electron-poor dienophiles and the Jt-orbital of the facing aromatics, which would lead to a stabilization of the transition state, while Nishio suggested that the selectivity is due to the attractive k/k or CH/jt interaction [53]. 

In 1995, these authors applied this methodology to the first total synthesis of the biosynthetically and unusual marine natural products, gracilins B and Thus, the key step of this synthesis was the enantioselective Diels-Alder reaction of 2-((trimethylsilyl)methyl)-butadiene with A-(2-iert-butylphenyl)maleimide in... 

The aqueous Diels-Alder reaction has also been used for bioconjugate studies. A Diels-Alder reaction of diene oligonucleotides with maleimide dieneophiles was used to prepare oligonucleotide conjugates in aqueous media under mild conditions (Eq. 12.39).102 A Diels-Alder-type cycloaddition of an electronically matched pair of saccharide-linked conjugated dienes and a dienophile-equipped protein was the... 

The thermal Diels-Alder reactions of anthracene with electron-poor olefinic acceptors such as tetracyanoethylene, maleic anhydride, maleimides, etc. have been studied extensively. It is noteworthy that these reactions are often accelerated in the presence of light. Since photoinduced [4 + 2] cycloadditions are symmetry-forbidden according to the Woodward-Hoffman rules, an electron-transfer mechanism has been suggested to reconcile experiment and theory.212 For example, photocycloaddition of anthracene to maleic anhydride and various maleimides occurs in high yield (> 90%) under conditions in which the thermal reaction is completely suppressed (equation 75). 

Petrillo reported that the bis-acetoxymethylpyrrole 83 undergoes a sequential Diels-Alder reaction of the in situ generated 2,3-dimethylpyrrole with carbodienophiles (such as maleic anhydride, maleimide, ethyl maleate, fumaronitrile, and ethyl acrylate) to afford the octahydrocarbazoles 84 which can be oxidized with DDQ to the corresponding carbazole derivatives . 

On the other hand, Hird and colleagues145 studied the Diels-Alder reactions of resin-bound 2-amino-1,3-butadienes with several iV-substituted maleimides and nitrostyrenes. 

Recently, Tan reported related bicyclic guanidine 20 as a chiral Br0nsted base to promote the highly enantioselective Diels-Alder reaction of various anthrones and maleimides (Scheme 5.41) [75]. Interestingly, use of dithranol led to the exclusive formation of the enantio-enriched Michael adducts. 

Diels-Alder reactions of 1,2-dihydropyridines with reactive dienophiles such as azo compounds and maleimides are also known (76JHC481). 

The Diels-Alder reaction of pyrrole-3-carboxyhc esters with TV-methyl- and N-phenyl-maleimides yield exclusively endo adducts.243 The Diels-Alder reaction of... 

Tetradehydrodianthracene undergoes 4 + 2-cycloaddition with electron-deficient dienes such as 1,2,4,5-tetrazines.263 The Diels-Alder reactions of [2>3]ortho-anthracenophanes with iV-(p-nitro, chloro, or methoxy-substituted phenyl)maleimides yield approximately equal quantities of inside and outside adducts.264 The photooxidation of bulky water-soluble 1,4-disubstituted naphthalenes with singlet oxygen yields both the expected 1,4- and the unexpected 5,8-endoperoxides.265... 

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. 

DFT theory at the B3LYP/6-31G(d,p) level was used to investigate the Diels-Alder reactions of o-quinone methides with various ethenes. Calculations show that solvent decreases the activation energy and increase the asynchronicity.116 The Diels-Alder reaction of ortho-quinone methides derived from 3//-1,2-benzoxathiole 2,3-dioxides with maleimides produces chroman 2,3-dicarboxylic acid derivatives.117... 

A series of compounds of the type 120 was prepared by the condensation of ai-ferrocenyl aliphatic acids with aromatic o-diamines.115 The Diels-Alder reaction of 121 (R = H or CH3) with various N-substituted maleimides gave a series of compounds of the type 122.116 Only the endo isomers were formed. A number of additional nitrogen-... 

The Diels-Alder reaction of 121 with maleic anhydride proceeds as noted earlier for maleimides.116 Ferrocenecarboxaldehyde and homo-phthalic anhydride have been condensed to give 174.96,97... 

Asymmetric Diels-Alder reactions of 1-p-tolylsulfinyldienes 161 with AT-methyl-maleimide (NMM) were completely stereoselective both under thermal and catalyzed conditions [142], yielding the same compounds endo-162 as sole... 

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]. 

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