Enamines cyclopentanone reaction, pyrrolidine

Problem 23.17 What products would result (after hydrolysis) from reaction of the enamine prepared from cyclopentanone and pyrrolidine with the following a, -unsaturated acceptors (a) Ethyl propenoate (b) Propenal (acrolein)... 

Experimental evidence, obtained in protonation (3,6), acylation (1,4), and alkylation (1,4,7-9) reactions, always indicates a concurrence between electrophilic attack on the nitrogen atom and the -carbon atom in the enamine. Concerning the nucleophilic reactivity of the j3-carbon atom in enamines, Opitz and Griesinger (10) observed, in a study of salt formation, the following series of reactivities of the amine and carbonyl components pyrrolidine and hexamethylene imine s> piperidine > morpholine > cthyl-butylamine cyclopentanone s> cycloheptanone cyclooctanone > cyclohexanone monosubstituted acetaldehyde > disubstituted acetaldehyde. 

The reaction of methyl propiolate (82) with acyclic enamines produces acyclic dienamines (100), as was the case with dimethyl acetylenedicarboxylate, and the treatment of the pyrrolidine enamines of cycloheptanone, cyclooctanone, cycloundecanone, and cyclododecanone with methyl propiolate results in ring enlargement products (100,101). When the enamines of cyclohexanone are allowed to react with methyl propiolate, rather anomalous products are formed (100). The pyrrolidine enamine of cyclopentanone forms stable 1,2-cycloaddition adduct 83 with methyl propiolate (82). Adduct 83 rearranges to the simple alkylation product 84 upon standing at room temperature, and heating 83 to about 90° causes ring expansion to 85 (97,100). 

N-Methyl-2-hydroxypyrroIidine (246) is derived biosynthetically from ornithine (245). It functions as a source of the N- methylpyrrolinium ion (247), which in turn functions as a precursor of alkaloids such as tropine (248). The pyrrolidine enamine of cyclopentanone undergoes an interesting ring closure reaction with DMAD, resulting in the formation of a pyrrolizine (Scheme 92) (78TL1351). 

Mono-benzoyldiimides such as 177 behave in a relatively normal manner, reaction with the pyrrolidine enamine of cyclohexanone (or cyclopentanone) giving the oxadiazine 178355 (Scheme 181). Reaction of dimethyl azodicarboxylate with / -disubstituted aldehyde enamines is reported to give the 1,2-diazetidine 179 and hence the aldehyde 180 on hydrolysis356", dibenzoyldiimide gives the oxadiazine 1813566 (Scheme 181). The ethoxycarbonyl aroyl diimide 182 reacts to give oxadiazine 183 exclusively357 (Scheme 182). 

Application of the dimethyl acetylenedicarboxylate reaction to enamines of cyclic ketones gave similar results the pyrrolidine enamines of cyclopentanone and a-tetralone gave the ring-expanded products (60 and 62, respectively) in toluene, and pyrrolizidines (61 and 63, respectively) in methanol (equation 32)53. 

Methyl jasmonate (218) has a //arris-locked, 2,3-disubstituted cyclopentanone structure.297 The synthetic route devised by Sisido and co-workers, outlined in Scheme 34, is direct and requires no isomer separation.298) Reaction of the pyrrolidine enamine of methyl 2-oxycyclopent-l-yl acetate (214) with 3-bromo-2-penta-none in toluene gave 215 after hydrolysis. An intramolecular aldol condensation afforded 216 (note double bond migration) whose epoxidation followed by treat-... 

Enamines can undergo reactions in which the iS-carbon acts as a carbanion. When pyrrolidine enamines of cyclopentanone and cyclohexanone were reacted with diethyl 2-vinylcyclopro-pane-l,l-dicarboxylate (1), a 1,7-addition was observed due to the attack of the C-nucleophile on the terminal carbon atom. ... 

PyrrolidinoaiamiMes. Review. Pyrrolidinoenamines of cyclohexanone and cyclopentanone can be prepared in about 82% yield by reaction of the ketone and pyrrolidine neat or in ether at room temperature. Under these conditions l-benzyl-3-pyrrolidinone was converted into the enamine (1) in 68% yield. 

The reaction of NO with the double bonds of enamines also produces compounds containing the diazeniumdiolate functional group bound to carbon, and some of the compounds prepared in this way have the potential to serve as spontaneous NO donors [43]. The compounds chosen for study were enamines 1-4 derived from condensation of cyclopentanone or cyclohexanone with morpholine or pyrrolidine. When these enamines were dissolved in acetonitrile and treated with NO gas (5-atm pressure) at room temperature, a vigorous exothermic reaction resulted, accompanied by high uptake of NO and formation of a brown precipitate. Attempts to isolate the solid precipitates often resulted in rapid decomposition, with the release of large volumes of gaseous NO. At -78 °C in diethyl ether, the reaction of 4-(l-cyclohexen-l-yl) morpholine (IX) afforded a good yield of crystalline NO addition product (X) ... 

Cyclopentanone derivatives 50 and 53 are stereoselec-tively obtained by the reaction of Fischer alkenyl carbene complexes 47 with chiral pyrrolidine enamines 48 (Scheme 5.12) [21]. The R -substituent on the pyrrolidine... 

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