3.4- Dihydro-5-methyl-2//-pyrrole

DEPMPO 2-Diethoxyphosphoryl-2-methyl-3,4-dihydro-2H-pyrrole-l-oxide... 

Methyl 3-acyl-l-diphenylmethyleneamino-4,5-dioxo-4,5-dihydro-l//-pyrrole-2-carboxylates 489 are formed from 488 and oxalyl chloride in good yields. Preparative thermolysis of these compounds at 130-140°C gives mixtures of dipyrazolo[l,2- l,2- [l,2,4,5]tetrazines 491 as major products and pyrazoles 492 as minor hydrolytic by-products. The intermediacy of mesoionic compound 490 is expected (Scheme 83) <2004T5319>. 

The allylically activated chiral methanimidamides are more reactive and can be prepared from 2,5-dihydro-l//-pyrrole or 1,2,5,6-tetrahydropyridine by heating with a chiral auxiliary substituted methanimidamide in toluene. Deprotonation of the more acidic 1 -iminomethy 1-2,5-dihydro-1//-pyrrole with butyllithium was complete after a few minutes, even at — 100 °C41. Alkylation afforded a mixture of regioisomers, 2-alkylated 2,5-dihydro-l //-pyrrole 1 (n = 1) and 3-alkylated 2,3-dihydro-l//-pyrrole 2 (n = 1), the former strongly predominating (about 92 8). During hydrazinolysis of the 2-substituted 2,5-dihydro-1 //-pyrrole 1 (n = 1) the minor product decomposed, thus separation of the regioisomers was unnecessary. About 80-85% of the chiral auxiliary (S)-l- m-butoxy-3-methyl-2-butanamine was recovered after hydrazinolysis. 

Die reduktive Aminierung von 2-(3-Oxo-alkyl)-l,3,4-oxadiazolen verliiuft analog unter intra-molekularer Ringtransformation uber 2-(2-Acyl-hydrazino)-5-methyl-4,5-dihydro-3H-pyrrole (33-54%) zu 5-Methyl-6,7-dihydro-5H-[Pg.620]

Die Umsetzung von 3,4-Dinitro-l-methyl-pyrrol mit eincm UberschuB an sekundaren Aminen wie Piperidin oder Morpholin ergibt 2,3-Dipiperidino(b7.w. Dimorpholino)-l-me-thyl-4-nitro-2,3-dihydro-pyrrol (85 bzw. 87%)z. 

Generation of the iminyl radical 184 in the above experiment was confirmed by an intramolecular radical trapping experiment. Reaction of l-phenylhept-6-en-3-one 0-2,4-dinitrophenyloxime (87) with m-cresol and NaH afforded 2-methyl-5-(l-phenylethyl)-3,4-dihydro-2H-pyrrole (88), which is the addition product of iminyl radical 187, obtained in 27% yield (Scheme 40). 

Eisen 0/5-Cyclopentadieny])-dicarbonyl-(2-methyl-4,5-dihydro-3H-pyrrol-5-yl-methyl]-E18, 322 (Cyclisierende NH3-Add.)... 

A new spin-trap, 5-(diethoxyphosphorylmethyl)-5-methyl-4,5-dihydro-3H-pyrrole N-oxide (48), " and its hydroxyl- and superoxide-spin adducts, have been compared with the analogues obtained with 5-(diethoxyphosphoryl)-5-methyl-4,5-dihydro-3H-pyrrole N-oxide (49 DEPMPO) and with 5,5-dimethyl-1-pyrroline N-oxide (50 DMPO), and overall the spin trapping behaviour of 48 was found to be more similar to that of DMPO than DEPMPO. 

Diazirines, which on heating or irradiation are converted into carbenes either directly or via the corresponding diazo compound, have been infrequently employed for the preparation of monoarylcyclopropanes. One of the few reports involved 3-(l-naphthyl)-3/f-diazirine. When this compound was irradiated in a mixture of acetonitrile and acrylonitrile, carbene addition to the C-C double bond took place, yielding a mixture of cis- and /ranj-l-cyano-2-(l-naph-thyl)cyclopropane (1) together with the cis- and trans-isomers of 4-cyano-5-methyl-2-(l-naph-thyl)-3,4-dihydro-2//-pyrrole (2). ... 

Roubaud, V., Mercier. A.. Olive, G., Le Moigne, F., and Tordo, P., 5-(Diethoxyphosphorylmethyl)-5-methyl-4,5-dihydro-37/-pyrrole A-oxide. Synthesis and evaluation of spin trapping properties, J. Chem. Soc.. Perkin Trans. 2. 1827, 1997. 

JV-Phenyl- or A-methyl-C-phenyl nitrones with (/ )-4-vinylsulfmyltoluene react with complete stereoselection in a process involving only the. Si-face of the alkene88. Cycloaddition of 4,5-dihydro-3//-pyrrole 1-oxide to unsaturated esters of chiral alcohols derived from camphor occurs with poor enantiofacial selection on the nitrone, but high diastereofacial preference on the alkene89. 

Thermolysis of methyl l-methyleneamino-4,5-dioxo, 5-dihydro-lW-pyrrole-2-carboxylates 123 led to substituted dimethyl 3,9-dioxo-l,5,7,ll-tetrahydro-lA/,7A/-dipyrazolo l,2-a r,2 -<3 ][l,2,4,51tetrazine-l,7-dicarboxylates 124 <04T5319>. 

C.G. Overberger, K.-H. Davidu. J.A. Moore, Macromolecules5, 368 (1972) die untersuchte Verbindung, 2-Carboxy-5-methyl-3,4-dihydro-2H-pyrrol, wurde auf einem anderen Weg hergestellt. 

Similarly, heating of methyl 3-acyl-l-(diphenylmethyleneamino)-4,5-dioxo-4,5-dihydro-l//-pyrrole-2-carboxylates 96 gave the corresponding dimethyl 2,8-diacyl-3,9-dioxo-5,5,ll,ll-tetraphenyl-3,5,9,lTtetrahydrodipyrazolo[l,2- 7 l, 2 -i [l,2,4,5]tetrazine-l,7-dicarboxylates 99 in good yields. The proposed mechanism involves thermal decarbon-ylation to give the ketene intermediate 97, which cyclizes into the azomethine imine 98, followed by dimerization (Scheme 24) <2004T5319>. 

Electrophilic attack on the 2-position of pyrroles has been a fruitful route into pyrrolo-1,4-diazepines. Treatment of o-aminobenzylpyrrole (131) with methyl glyoxalate or its methoxy hemi-acetal in methanol furnished methyl 10,ll-dihydro-5//-pyrrol 2,l-c]-l,4-benzodiazepine-ll-car-boxylate (132) in 75% yield (Equation (5)) <84JHC833>. 

A solution of 200 mg sulfide (139 /u.mol) and 0.148 mL triethyl phosphite (142 mg, 850 /xmol) in 2 mL dry benzene was degassed and heated to 120 °C for 72 h in a sealed tube. The mixture was concentrated and chromatographed on aluminium oxide (activity III-IV, linear gradient of 10-20% EtOAc/hexane) to give 177 mg [2/ ,35, 45, 5(2Z,35, 45 )]-2, 3-dimethyl-5-[(3-methyl-5-oxo-3-(2-(trityloxy)ethyl)-4-(3-(trityloxy)propyl)pyrrolidin-2-ylidene)methyl]-3-(2-(trityloxy)ethyl)-4-(3-(trityloxy)-propyl)-3,4-dihydro-2H-pyrrole-2-carbonitrile as a mixture of diastereoisomers ( 36 6 6 1), in a yield of 90%. Diastereomer-ically pure material was obtained by HPLC (Nuc 50-10, 10 1 2 hexane/MeOAc/diethyl ether, +20% hexane, 10 mL/min) to give 130 mg pure A-B-semicorrin as an amorphous solid, in a yield of 67%. 

Representative procedure for the gold-catalyzed cycloisomerization of protected a-aminoallenes. 2-Benzyloxymethyl-5-isopropyl-3-methyl-l-(toluene-4-sulfonyl)-2,5-dihydro-lH-pyrrol ... 

Hydroxy-3-methyl-2-butenenitrile, H-80198 1 -Methyl-1,2-dihydro-3//-pyrrol-3-one, in... 

Ethyl 3-methyl l-(4-methoxyphenyl)-4-((4-methoxyphenyl)amino)-5-oxo-2,5-dihydro-1//-pyrrole-2,3-dicarboxylate (4a) Light yeUow solid, mp 122-123 °C yield 72%... 

Ethyl 3-methyl 4-(benzylammo)-l-(4-bromophenyl)-5-oxo-2,5-dihydro-l//-pyrrole-2,3-dicarboxylate (6a) White solid, mp 127-128 °C yield 40%... 

---