Maleimide adducts

The octamethyl derivative 39 (syn configuration) is obtained on refluxing the pentacyclic maleimide adduct in bis(2-methoxyethyl) ether (diglyme).19... 

Sample preparation 5 mL Urine + 2 mL 500 mM pH 7.0 phosphate buffer -I- 0.5 mL 20 mg/mL p-bromophenaaqueous layer and add it to 100 p-L 2% tributylphosphine in MeOH, heat at 50°for 30 min, wash with 6 mL hexane, add 200 p,L 0.2% N-(4-dimethylamino-3,5-dinitrophenyDmaleimide in acetone to the aqueous layer, mix, let stand at room temperature for 5 min, wash with 6 mL hexane, discard the hexane layer, acidify the aqueous layer with about 200 pL 2 M HCl, extract twice with 6 mL portioiis of benzene (Caution Benzene is a ceircmogen ). Combine the organic layers and add 10 pg IS, evaporate to dryness imder reduced pressure, reconstitute the residue in 200 pL MeOH, inject a 5-20 pL aliquot. (Free captopril is derivatized as its p-bromophenaQrl bromide adduct then oxidized captopril is reduced and derivatized as its N-(4-dimethylamino-3,5-dinitro-phenyl)maleimide adduct.)... 

Thebaine-maleimide adducts have been prepared, and the Diels-Alder reaction of thebaine with cyclic azo-dienophiles has been investigated. " Nitrosation of thebaine hydrochloride with nitrosyl chloride or pentyl nitrite in methanol or ethanol gives 7-hydroxyiminoneopinone dimethyl or diethyl acetal. " The chemistry of 14-bromocodeinone and its dimethyl acetal has been studied in some detail, including catalytic hydrogenation, "" methanoly-sis, " debromination, "" dehydrobromination, " and solvolysis.Efforts are continuing in the preparation of novel analgesics in the morphine-thebaine series. 

Table 9.2. Spectral Properties of Maleimide Adducts (Sharpless and Flavin, 1966) ...

Pyrrolidine-maleimide adduct Piperidine-maleimide adduct Benzylamine-A -phenyl maleimide adduct Glycylamide-N-ethyl maleimide adduct Glycylamide-A -phenyl maleimide adduct 1715 1712 1709 1706 ) 1672J 1718] I68IJ 1634 1603 1771 1770 1779 1779 1786... 

Retention time 7 (free captopril (as p-bromophenacyl bromide adduct)), 8 (oxidized captopril (as N-(4-dimethylamino-3,5-dinitrophenyl)maleimide adduct))... 

The Tg of these thermoplastic materials was 30-105 C (i.e., higher than those of the crosslinked counterparts) because incorporation of amide groups in their macromolecules resulted in a decrease in chain flexibility associated with intermolecular C=0 H-N hydrogen bonds. It was, moreover, verified that their thermal reversibility was limited to furan-maleimide adducts (i.e., only half of the DA couplings), with the others being thermally stable. 

It should be noted that although no distinction is made between the endo and exo stereoisomers (Fig. 12.25) of furan-maleimide adduct (assuming that their thermal behavior is at least similar if not equal), differences in thermal reversibility (rDA, DA) can have an important in uence on the material properties, especially in the case of thermoremendable polymers and networks. For instance, by breaking only the covalent bonds of the endo DA-isomers inside the network imder mild conditions and reforming them in a less stressed state, stresses can be relaxed. Important material properties such as durability, adhesion to other materials, appearance of micro-voids and micro-cracks, etc., can be improved (Canadell et al., 2010). 

MA Diels-Alder reactions, 130 MA-epoxide reaction, 508 maleimide-amide reaction catalysts, 512 MA polymerization initiators, 256 2-Iminocyclopentanedithiocarboxylic acid MA reaction, 51 maleic diamide adduct, 51 maleimide adduct, 51... 

Neopentyl glycol, polyesters use, 494 Nickel, MA bisadduct, 212 Nickel carbonyl, MA complex, 212 Nickel chloride, MA distillation additive, 22 Nickel oxide, oxidation catalyst, 31, 36 Nicotinic acid, use in polyesters, 490 Nitrile imines, dimethyl fumarate adduct, 225 Nitrile oxides, MA adducts, 225 Nitriles, Michael addition to maleates, 64 Nitrile sulfides MA adducts, 225 maleimide adducts, 227 p-Nitroaniline, permaleic acid oxidation, 77 Nitrobenzene, 180 ene reaction solvent, 166 Friedel-Crafts acylation solvent, 93, 97 2-Nitrofuran, 127... 

MA Diels-Alder adduct, 127 maleimide adducts, 128 oxidation to maleimide, 88... 

Trimethylsilylaminomaleimide, A -methyl, synthesis procedure, 223 Trimethylsilyl azide aldehyde reaction, 223 MA adduct, 223 MA reaction mechanism, 224 jV-methyl maleimide adduct, 223 jV-phenyl maleimide adduct, 223 Trimethylsilylvinyl ketene, MA Diels-Alder adduct, 107... 

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). 

Dihydropyridines 8 react with dienophiles such as A -phenyl maleimide (2) and l,2,4-triazoline-3,5-dione 9 to give the Diels-Alder adducts 10 and 11, respectively (76JHC481). Fowler observed that when a mixture of 1,2- and 1,4-dihydropyridines was treated with maleic anhydride (12), only 1,2-dihydro-pyridines yielded the Diels-Alder adducts 13, whereas the 1,4-dihydropyridines showed no reactivity with 12 (72JOC1321) (Scheme 1). 

Indolo[3,2-fl]pyrrolo[3,4-c]carbazoles 120 have been obtained in one step from indole and the corresponding maleimides in acetic acid, with coformation of the Michael adducts 121 (Scheme 15). This reactitai required careful temperature control in order to obtain the desired product ratios. An alternative independent synthesis of compounds 120 could also be accompKshed from 2,3 -biindolyl (115) andsuitable maleimides in hot acetic acid (99T2363). The system 120 where R = H has also been reported as a minor product during studies toward a synthesis of the alkaloid arcyriaflavin A (95TL2689). 

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]. 

The Diels-Alder adduct, anhydride 63, on treatment with hydrazine hydrate in acetic acid for 20 min yielded 252 which on keeping in acetic acid for further 8 h gave the imide derivative 253. This adduct, imide 253, underwent retro-Diels-Alder reaction to eliminate furan giving amino maleimide derivative 254 (Scheme 45) <2005J OC4553>. 

Differently substituted pyrrolopyrroles can be constructed from a 1,3-dipolar cycloaddition, between the adduct from glycines and aldehydes and maleimides. Then, for example, the initially formed iV-allyl-o-bromophenyl-substituted pyrrolopyrrole mixture, 223, + 224, can then undergo an intramolecular cyclization in the presence of catalytic palladium(O) to give the pyrroloindolizine 225 <1991TL1359> (Scheme 61). 

Finally, we should indicate that we have not ruled out the possibility that there is a contribution to initiating photopolymerization in maleimide/vinyl ether systems from an exciplex type complex between an excited state maleimide and ground state vinyl ether. A biradical formed from such a complex might initiate free radical polymerization in lieu of cyclization to form a 2 + 2 adduct. However, we note that at present we have no evidence for such a reactive exciplex. 

In the reaction of fused aziridines with alkene dipolarophiles, the opportunity for stereoselectivity as well as facial selectivity arises since exo- or entfo-isomers can be formed (Scheme 10). In practice, maleic anhydride 6, A-methyl maleimide and JV-phenyl maleimide each reacted exo-stereoselectively with TV-benzyl aziridine 69 to form adducts of type 71 (Scheme 10b), the stereochemistries of which were confirmed by NOE measurement between Hb and He. Similar reaction of the Y-phenyl aziridine 67 with N-Ph maleimide gave a 1 1 mixture of endo-adduct 72 and exo-adduct 73 (Scheme 10c). Adducts 68, 71-73 all exhibited a low-field methano-bridge proton (Ha) in the range 5 3.06-3.60 confirming the syn-facial stereochemistry of the two bridges. 

Nitrones derived from cyclic acetals of D-erythrose (479) and (689) and of D-threose (480) and (690), reacted with N -phenylmaleimide D15a to afford the corresponding diastereomeric isoxazolidines (691-706) (Scheme 2.295). The stereoselectivity is dependent on the substituents in the nitrone. In the case of nitrones (479) and (689) the cycloaddition is exo-selective. It was observed that microwave irradiation decreased the reaction times of the cycloadditions dramatically. For example, for nitrone (689) and dipolarophile D15a the reaction time decreased from 11 h to 8 min and for nitrone (690) and D15a it decreased from 3 h to 10 min. Moreover, microwave irradiation reversed the ratio of erythro-frans/erythro-r/.v adducts from 63 37 to 39 55, see compound (689). Cycloadditions of the chiral maleimides D15b and D15c are less stereoselective (817). 

Monoclonal antibodies to sulfhydryl-terminated PAMAM dendrimers [9,10] could be bound to sulfhydryl-terminated PAMAM dendrimers under stoichiometric conditions favoring complexes of one antibody to one dendrimer. After binding, the exposed sulfhydryl surface may be derivatized to eliminate SH groups. Antibody and dendrimer complexes are then dissociated and the patterned dendrimers are isolated. Only areas masked by the antibody retain sulfhydryl groups, and can therefore be differentially derivatized (to a gold adduct, or to maleimide-linked macromolecules, for instance). 

The reactions of A-phenyl a-r-butyl nitrone (PEN) with maleimides, maleic anhydride, and diethyl maleate have been studied by EPR and two types of spin adduct detected. They arise from the reductive addition of PEN to the alkenes and the degradation product of DEN (2-methyl-2-nitropropane). The deuterium and muonium kinetic isotope effects for the addition of the hydrogen atom to a variety of alkenes have been determined experimentally and theoretically. ... 

Triphenylthieno[3,4-c]pyrazole (414) can be presented as a hybrid of dipolar-contributing azomethine imine ylide (415) or thiocarbonyl ylide canonical forms 416. Upon reacting this ylide with electron-poor olefins, it behaved like a thiocarbonyl ylide. Thus, with maleimide, a mixture of endo (419) and exo adducts (420) were obtained (74JA4276), which resulted from addition at the thiocarbonyl moiety. The reaction of 414 with dimethyl acetylenedicarboxylate gives the desulfurized indazole 418 in addition to the adduct 417 (Scheme 41). 

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. 

The ability to form adducts was also found in the so-called non-classical thienothiophene (4). As described above (see Section II,B), the sulfoxide of 4,6-dimethyl-l//,3i/-thieno[3,4-c]thiophene (143) and l,3,4,6-tetraphenylthieno[3,4-c]thiophene 049) react with A -phenyl-maleimide to form endolexo pairs of adducts 144, 145 and 150,... 

Scheme 1.64). The Ag(I)-mediated cyclization afforded dipole 306 for 1,3-dipolar cycloaddition with methyl vinyl ketone to yield adducts 307 and the C(2) epimer as a 1 1 mixture (48%). Hydrogenolytic N—O cleavage and simultaneous intramolecular reductive amination of the pendant ketone of the former dipolarophile afforded a mixture of alcohol 308 and the C(6) epimer. Oxidation to a single ketone was followed by carbonyl removal by conversion to the dithiolane and desulfurization with Raney nickel to afford the target compound 305 (299). By this methodology, a seven-membered nitrone (309) was prepared for a dipolar cycloaddition reaction with Al-methyl maleimide or styrene (301). 

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