2//-Pyrrole 1-oxide, 3,4-dihydro

Thieno[2,3-d ]pyrimidin-4(3 H) -one, 3-methyl-synthesis, 4, 1017 Thieno[2,3-d ]pyrimidin-4-ones synthesis, 4, 1017, 1018, 1022 Thieno[2,3-6]pyrrole, 5-aryl-synthesis, 6, 1009 Thieno[2,3-6]pyrrole, N-benzyl- H NMR, 4, 1042 UV spectra, 4, 1044 Thieno[2,3-c]pyrrole, N-ethyl-UV spectra, 4, 1044 Thieno[3,2-6]pyrrole, 5-aryl-synthesis, 6, 1009 Thieno[3,2-6]pyrrole, N-benzyl- H NMR, 4, 1041, 1042 lithiation, 4, 1051 UV spectra, 4, 1044 Thieno[3,2-6]pyrrole, 2,3-dihydro-desulfurization, 6, 984 oxidation, 6, 981... 

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

The influence of substituents on regioselectivity was studied by using a model nitrone 3,4-dihydro-2,2-dimethyl-2/f-pyrrole 1-oxide (DMPO, 256) with different alkylidenecyclopropanes substituted with phenyl (156), electronreleasing (270 and 271) and electron-withdrawing groups (52, 272 and 4) [67,... 

AMI calculations have been used to explain the regioselectivities of the intermolecular asymmetric 1,3-dipolar cycloadditions of 2,2-dimethyl-3,4-dihydro-2//-pyrrole A-oxides with chiral a, /i-unsaturatcd esters.96 MO calculations have shown that only in-plane aromaticity is operating in transition structures+associated with the... 

Simple pyrroles frequently give complex breakdown products. Oxidation with oxygen (UV-irradiation, a photosensitizer, or an radical initiator) produces hydroxypyrrolones <1991JOC6942, 1999TL4519, 2002TA601>. For example, pyrrole 152 (30 C) leads to 5-hydroxy-l,5-dihydro-27/-pyrrol-2-one 153 <2003T8499>. 

Reaction of 3,4-dihydro-6,7-dimethoxyisoquinoline with the propargyl Grignard reagent leads to the cyclic homopropargylamine, which on silver(I)-mediated oxidative cyclization affords 5,6-dihydro-8,9-dimethoxypyrrolo[2,l-a]isoquinoline. Che-moselective hydrogenation of the pyrrole ring provides racemic crispine A (three steps, 24 % overall yield). 

Although conceptually similar, the direct coupling of carbonyl compounds with pyrroles (Scheme 141) using a Cu(ii) oxidant probably differs mechanistically from the intramolecular cyclization of pyrrole 718 to 2,3-dihydro-l//-pyrrolizine 719 (in 65% yield as a 4.5 1 mixture of diastereomers) using Fe(lll)-based oxidant (ferrocenium hexa-fluorophosphate) (Scheme 142) <2006ARK310>. 

The A -(pyrrol-2-yl)carbamates 860 are oxidized smoothly by air to a mixture of the A -(5-hydroxy- 862 and 5-hydroperoxy- 863 -l,5-dihydro-2/7-pyrrol-2-yliden)carbamates (in 63% and 8% yield, respectively, when R = H, = Bn) (Scheme 166) <1997TL1293>. Oxidation with pure oxygen gives the same products in a yield of 47% and... 

The use of 1,1-diiodomethane as an electrophile in the Birch reduction (with lithium in liquid ammonia) of electron-deficient pyrroles 915 furnished pyrrolines 916 (in high to excellent yields), which provided access to the synthetically important functionalized 5,6-dihydro-2(l//)-pyridinones 917 (via radical ring expansion), substructures commonly found in biologically active natural products (Scheme 177) <2004CC1422>. 2-(Chloroalkyl)-substituted pyrrolines 919 were duly prepared by the reductive alkylation (with l-chloro-3-iodopropane or 1-chloro -iodobu-tane) of electron-deficient pyrrole 918. Allylic oxidation then furnished lactams 920 (Scheme 178). 

A tandem carbonylation-cyclization radical process in heteroaromatic systems bearing electron-attracting substituents such as l-(2-iodoethyl)indoles and pyrroles 970 result in the formation of 2,3-dihydto-l//-pyrrolo[l,2- ]indol-1-ones and 2,3-dihydro-l//-pyrrolizin-l-ones 974 (Scheme 188). The AIBN-induced radical reaction of compounds 970 with Bu3SnH under pressure of CO suggests that the acyl radical 972, derived from radical 971 and CO, would undergo intramolecular addition to C-2 of heteroaromatic system, and the benzylic radical 973 so obtained, upon in situ oxidation would produce final product 974 <1999TL7153>. 

The homologous compound 983 gave the expected 6,7-dihydto-8(5//)-indolizinone 985 in moderate yield and 2,3-dihydro-177-pyrrolizine 984, resulting from competitive 5-o ti-cyclization of the alkyl radical, in low yield (Equation 233) <2000TL3035>. The formation of 6,7-dihydro-8(5//)-indolizinone 986, the product derived from radical attack at C-5, is interesting, and has precedence in oxidative intramolecular radical alkylation of pyrrole 983... 

New fused 6,8a-dihydro-4/7-pyrrolo[l,2- ][l,2,5]oxadiazines 1176 and 5,7a-dihydro-37/-pyrrolo[l,2- ]imidazole 1-oxides 1177 were obtained via hetero-Diels-Alder reactions ([4-1-2] and 1,3-dipolar) adding 277-pyrrole 1174 to substituted nitrosoalkenes [CH2=C(R)N=0], generated in situ thorough base-mediated dehydrohalogenations of ot-bromooximes 1175 (Equation 268) <2002T1507>. 

Oxid), 1412 (NH - N-oxid) 3H-Pyrrol-l-oxid 2-Methyl-4,5-dihydro- E14b, 146 (aus N02-Keton) Pyrrolidin... 

H-Pyrrol 2-Amino-5-methyl-4,5-dihydro- -1-oxid X/4, 349 Pyrrolidin l-Hydroxy-5-imino-2-methyl- X/l, 440... 

H-Pyrrol 5-Ethenyl-2-methyl-4,5-dihydro- -1-oxid E14b, 1432 (aus Oxim intracycl. C,N-Bild.)... 

Propan 2-Isocyanat-2-phenylazo-E16d, 98 (oxidative Umlagerung) Pyridin 2-Aminocarbonyl-5-(4,5-dihydro-3H-pyrrol-2-yl)- E13/2, 1319 (SE)... 

Pyrrol l-Methyl-3-(l-methyl-2-pyrrolidinyl)-4,5-dihydro- E15/1, 655 (Amin-Oxid.)... 

H-Pyrrol 2-tert.-Butyl-5,5-dimethyl-3-hydroxamino-4,5-dihydro- -1-oxid El4b, 1471 (aus Nitro-keton)... 

Pyridin-1-oxid 6-Phenyl-3,4,5,6-tetrahydro- X/4, 323 3H-Pyrrol 3-Methoxy-2-phenyl-4,5-dihydro- E6a, 626 [R2N —... 

An example of a third-generation cycloadduct 187 was synthesized via alternating 1,3-dipolar cycloaddition and oxidation steps starting from 3,4-dihydro-2//-pyrrole 1-oxide and furan-2(5//)-one (Scheme 44) <1997T2979>. 

The preparation of a novel phosphonate containing 3,4-dihydro-2-H-pyrrole-1-oxide residue (216) has been reported. The synthesis of this solid and highly lipophilic spin trap is based on the addition of diethyl phosphite to pyrroline (217) and subsequent m-CPBA oxidation of phosphonate (218). (Scheme 59). The structure of the (218) was assigned using X-ray diffraction techniques. Its ability to react with different free radicals especially hydroxyl and superoxide was evaluated. ... 

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