2-Acetyl-3,4-dihydro-5//-pyrrole

Ci Coch, 2-acetyl-3,4-dihydro-5//-pyrrole [85213-22-5] characteristic odor of white bread crust... 

In order to achieve 2-nitration, acetyl nitrate may be used as the reagent, but unlike pyrrole a semi-stable adduct, 5-acetoxy-2,5-dihydro-2-nitrofuran, is formed as an intermediate product (Scheme 6.22). This eliminates acetic acid when treated with pyridine. Furan also undergoes initial bromination or chlorination (X = Br or Cl) in ethanol at -40 °C, but then addition of two ethoxyl units occurs with the expulsion of halide ion (Scheme 6.23). 

The reaction of 74 with 4-methylbenzenecarbonyl chloride 105 in the presence of triisobutylamine affords ethyl 10,11-dihydro-10-(4-tol uoy 1 (pyrrole [ 1,2-/4 [1,2,5 ]bcnzothiadi-azcpinc-l 1-acetate 5,5-dioxide 106 (Scheme 23) <1996FES425>. Acetylation of 74 was performed by reaction with acetic anhydride to give 107 <1996BMC837>. 

When pyrrole 987 was subjected to the usual reaction conditions, l-(2,3-dihydro-17/-pyrrolizin-5-yl)-l-ethanone 988 was obtained as the major product. The desired diketone 989 was isolated in very low yield together with a small amount of the unexpected sulfone 984 (Equation 234). This compound is formed by alkyl radical addition at C-5, and subsequent aromatization by the loss of an acetyl radical. When pyrrole 987 was reacted with BusSnH/AIBN in the absence of CO, dihydropyrrolizines 988 and 984 were isolated in 74% and 23% yields, respectively <2000TL3035>. 

FIGURE XIV-1 B The amide II, imide III, and lactam IV configurations in l-acetyl-3-ethyl-l,5-dihydro-4-methyl-2/f-pyrrol-2-one I. ... 

Chemical properties of the batrachotoxin fraction were assessed on a microscale. In retrospect it appears that most reactions resulted in loss of the pyrrole entity and hence a product which did not afford a positive Ehrlich reaction. These chemical reactions included catalytic hydrogenation with palladium on charcoal, reduction with lithium aluminium hydride, treatment with acidic methanol, oxidation with manganese dioxide, treatment with acid, reaction with 2,4-dinitrophenylhydrazine, and exhaustive methylation with methyl iodide. An Ehrlich-positive methiodide could be obtained under milder conditions with methyl iodide. Acetylation of the batrachotoxin fraction with acetic anhydride and pyridine afforded two Ehrlich-positive 0-acetyl derivatives. Reaction with methoxyamine afforded an Ehrlich-positive 0-methyloxime. Reduction with sodium borohydride afforded an Ehrlich-positive dihydro-derivative. This product apparently isomerizes to other dihydro-compounds (257). Autoxidation, a serious problem during isolation of batrachotoxin, led to Ehrlich-negative products. 

Acetyl-1,5-bis( 1,2-dihydro-1,5-dimethyl-3-oxo-2-phenyl-4-pyrazolyl)formazan, A-00014 1 //-Pyrrole-2-carbothioic acid S-Me ester, in P-00437 1//-Pyrrole-2-carbothioic acid 1-Me, 5-Me ester, in P-00437 2,9-Dimethyl-1,10-phenanthroline A-Oxide, in D-00880... 

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