N Phenylmaleimide

Benz[/]isoindole 10 exists, on the basis of spectroscopic examination, predominantly in the benzenoid tautomeric form 10b, although the formation of the Diels-Alder adduct with N-phenylmaleimide suggests the presence of a small amount of the o-quinoid tautomer 10a (78JOC4469). 

The validity of the model was demonstrated by reacting 35 under the same reaction conditions as expected, only one diastereoisomer 41 was formed, the structure of which was confirmed by X-ray analysis. When the vinylation was carried out on the isothiazolinone 42 followed by oxidation to 40, the dimeric compound 43 was obtained, showing that the endo-anti transition state is the preferred one. To confirm the result, the vinyl derivative 42 was oxidized and the intermediate 40 trapped in situ with N-phenylmaleimide. The reaction appeared to be completely diastereoselective and a single diastereomer endo-anti 44 was obtained. In addition, calculations modelling the reactivity of the dienes indicated that the stereochemistry of the cycloaddition may be altered by variation of the reaction solvent. 

C ( propyl) N phenylmtrone to N phenylmaleimide, 46, 96 semicarbazide hydrochloride to ami noacetone hydiochlonde, 46,1 tetraphenylcyclopentadienone to diphenyl acetylene, 46, 44 Alcohols, synthesis of equatorial, 47, 19 Aldehydes, aromatic, synthesis of, 47, 1 /3-chloro a,0 unsaturated, from ke tones and dimethylformamide-phosphorus oxy chloride, 46, 20 from alky 1 halides, 47, 97 from oxidation of alcohols with dimethyl sulfoxide, dicyclohexyl carbodumide, and pyndimum tnfluoroacetate, 47, 27 Alkylation, of 2 carbomethoxycyclo pentanone with benzyl chloride 45,7... 

N Phenylhydroxylamine condensation, with benzaldehyde to form N,a-diphenylmtronc, 46,127 with n-butyraldehyde, 46, 96 Phenyl lsothiocyanate, 46, 21 Phenylhthium, 46, 109 N-Phenylmaleimide, conversion to 3-phenyl-3 -propylisoxazolidinc-... 

Bulky substituents make it possible to prepare a stable 8n-electron thiepin. For that purpose, the methoxycarbonyl groups of furanothiepin 6 (R = C02Me) are converted with methylmagne-sium bromide to the corresponding diol (R = CMe2OH) which reacts spontaneously with N-phenylmaleimide to give the thermally stable endo-thiepin 8.67 Quantitative desulfurization is achieved in the presence of triphenylphosphane. 

Dibenz[c,e]azepine 6-oxide, a cyclic nitrone (see Section 3.2.1.5.1.), yields crystalline 1,3-dipolar cycloadducts with phenylisocyanate (adduct yield 98 % mp 190-191 C) and with N-phenylmaleimide (adduct yield 86% mp 235-236°C).6... 

MA = maleic anhydride NPM = N-phenylmaleimide NQ = 1,4-naphthoquinone TONE = tetracyanoethylene... 

The cycloaddition of chiral, racemic and non-racemic alkoxybutadienes 109 with phenyltriazolinedione led to aza compounds [110] in high yield, with good facial selectivity (diastereomeric excess 87-92%) (Equation 2.31). The cycloadditions of the same dienes with N-phenylmaleimide require Lewis acid catalysis. 

Tetraene 141 has been converted into various complex polycondensed adducts by reacting with a variety of dienophiles such as maleic anhydride, N-phenylmaleimide, N-phenyltriazolinedione,p-benzoquinone and tetracyano-ethylene carried out under thermal conditions. All cycloadditions occurred facial-diastereoselectively from an outside attack and provided monocycloadducts which had an exceptionally close relationship between diene and dieno-phile and then underwent intramolecular cycloaddition [125]. The reaction between 141 and p-benzoquinone is illustrated in Scheme 2.53. 

A broad study on the MW-assisted Diels Alder reactions of 2H-pyran-2-ones 50 and 51 with 1,4-naphthoquinone 52 and N-phenylmaleimide 53 (Equations 4.3) supported on silica-gel, K-10 montmorillonite, fitrol and alumina was carried out by Samant and colleagues [41]. 

The Diels-Alder reaction of 2H-pyran-2-ones part IV - Microwave catalyzed Diels-Alder reaction of 4,6-disubstituted-2H-pyran-2-ones with 1,4-naphthoquinone and N-phenylmaleimide [41a]... 

An interesting phenomenon has been observed in the high pressure Diels-Alder reactions of the l-oxa[4.4.4]propella-5,7-diene (117) with 1,4-naphthoquinone, maleic anhydride and N-phenylmaleimide, where the diene 117 undergoes a rearrangement to the diene isomer 118 which, although thermodynamically less favored, exhibits a greater reactivity [40]. The reactivities of the three dienophiles differed since maleic anhydride and N-phenylmaleimide reacted only in the presence of diisopropylethylamine (DIEA) and camphorsulfonic acid (CSA), respectively (Scheme 5.15). The distribution of the adduct pairs shows that the oxygen atom does not exert a consistent oriental dominance on TT-facial selectivity. 

Tropone (125) and tropolone (130) reacted [44] with N-phenylmaleimide at high pressure (lOkbar) and gave a mixture of exo- and ewJo-adducts, 131 and 132, respectively (Equation 5.16). 

High-pressure organic chemistry. Part 17. Diels-Alder reaction of methyl palustrate with maleic anhydride and N-phenylmaleimide [87]... 

High-pressure Diels-Alder reaction of 1-methyl-2-(1H)-pyridones having a phenyl group with N-phenylmaleimide [94]... 

Interestingly, the cycloaddition of 2-azadiene 44 with N-methylmaleimide in 2.5m LT-DE gave predominantly exo-adduct in contrast to the thermal cycloaddition that is mainly enJo-selective (Scheme 6.27). A similar but not so dramatic increase in cxo-selectivity was also observed [47] for the cycloaddition of 44 with N-phenylmaleimide. The reaction is kinetically controlled, but the origin of the high cxo-selectivity observed in LT-DE is unclear the polar medium probably favors the more polar exo transition state. 

During investigation of the synthesis of benzocyclobutane 193, Cava and co workers found that o-quinodimethane 192, generated in the pyrolysis of 1,3-dihydrobenzo[c]thiophene 2,2-dioxide (191), can be trapped by N-phenylmaleimide to give N-phenyl-l,2,3,4-tetrahydronaphthalene 2,3-dicarboimide (194) (equation 125). 

Several other groups have employed a similar approach. Muthusamy and coworkers prepared cyclooctanoid ring systems such as 6/2-14 and 6/2-15, respectively, starting from 6/2-12 either with N-phenylmaleimide or dimethyl ethynedi-carboxylate as 1,3-dipolarophiles via the dipole 6/2-13 (Scheme 6/2.2) [190]. 

Another intramolecular ene-yne metathesis followed by an intermolecular metathesis with an alkene to give a butadiene which is intercepted by a Diels-Alder reaction was used for the synthesis of condensed tricyclic compounds, as described by Lee and coworkers [266]. However, as mentioned above, the dienophile had to be added after the domino metathesis reaction was completed otherwise, the main product was the cycloadduct from the primarily formed diene. Keeping this in mind, the three-component one-pot reaction of ene-yne 6/3-94, alkene 6/3-95 and N-phenylmaleimide 6/3-96 in the presence of the Grubbs II catalyst 6/3-15 gave the tricyclic products 6/3-97 in high yield (Scheme 6/3.28). 

Table 15. Reactions of 149 and 150 with maleic anhydride (115) and N-phenylmaleimide (116)... 

The allene 149 gave by reaction with maleic anhydride (entry 1) and N-phenylmaleimide (entry 2) the [2 + 2] adducts 155a, b as mixtures of two diastereoisomers [36], Nevertheless, their chemical yield was very low and competitive reactions, mostly [4 + 2] cycloadditions on a rearranged al-lylidenecyclopropane and on a primary 1 1 adduct derived from an ene reaction (see Sect. 2.1.2), prevailed. Allenes 149 and 563 cycloadded to tetracyano- and l,l-bistrifluoromethyl-2,2-dicyanoethylene (Table 45, entries 3-6) also selectively at the cyclopropyl substituted double bond in order to remove most of the ring strain [149a],... 

Chloro(hydroxyimino)methyl]-3-phenyl-l,2,3-oxadiazolium-5-olate-(3-phenylsydnone-4-carbohydroximoyl chloride) reacts in situ (through nitrile oxide) with N-arylmaleimides or 2-methyl-N-phenylmaleimide to give 5-aryl-3-(3-phenylsydnon-4-yl)-3a,6a-dihydropyrrolo[3,4-r/]isoxazole-4,6-diones or dame thyl-5-pheny l-3-(3-phenylsydnon-4-yl)-3a,6a-dihydropyrrolo[3,4-d]isoxazole-4,6-diones, respectively (265). 

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). 

C-( -propyl)-N-phenylnitrone to N-phenylmaleimide, 46, 96 semicarbazide hydrochloride to ami-noacetone hydrochloride, 46, 1 side-chain carbanions to arynes, 48, 55... 

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