Pyrroline-1-carbonyl group

A-methoxy-carbonyl-2-pyrroline 235 Michael reactions, nickel catalysis 97-8 monophospholanes with pendant f-BuS group 17,19... 

Intramolecular variations of a series of bifunctional derivatives lead to the formation of cyclic nitrones. Many pyrroline /V-oxide derivatives were obtained in the course of intramolecular interaction in situ between carbonyl and hydrox-ylamine groups, resulting from the reduction of a y-nitro group (Scheme 2.31) (Fig. 2.8) (238-253). 

We have shown that the ylids 3 react with a number of nucleophiles (3). In particular 3a and 3b react quantitatively with the alkylidene phosphoranes 5 to give 3-pyrrolines 6a and 6b as a mixture of diastereoisomers. The cyclisation occurs via an intramolecular Wittig reaction on the carbonyl of an ester group (M. In the same conditions, 2c reacts with 5 to give quantitatively the pyrrolines 7c (two diastereoisomers) as a result of a Wittig reaction on the carbonyl of the keto group in 3c. 

Hydroxy aldehydes or ketones normally exist in equilibrium with the corresponding 2-hydroxytetrahydrofurans, which afford 2,3-dihydrofurans on dehydration. Similarly, 7-aminoketones spontaneously yield pyrrolines. From a mechanistic viewpoint the-initial cyclizations may be regarded as being initiated by nucleophilic attack of the heteroatom upon the carbonyl group. While such reactions occur with facility, their synthetic applicability is largely determined by the accessibility of appropriate precursors. A selection of examples of this type of ring closure is provided in Scheme 12. 

FIGURE 14.28 The vinylogous relationship between the carbonyl and the amino group in pyrroline-3-ones gives them the reactivity of secondary amidesd ... 

The imine and iminium functional groupings are, of course, the nitrogen equivalents of carbonyl and O-protonated carbonyl groups, and their reactivity is analogous. The Mannich reaction of pyrrole produces dialkylaminomethyl derivatives, the iminium electrophile being generated in situ from formaldehyde, dialkylamine and acetic acid. There are only a few examples of the reactions of imines themselves with pyrroles the condensation of 1-pyrroline with pyrrole as reactant and solvent is one such example. N-Tosyl-imines react with pyrrole with Cu(OTf>2 as catalyst. ... 

Pyrroline-3-ones were used as peptidic bond surrogates by Hirshman and his group. In such compounds (Fig. 12.28), thanks to vinylogy, the carbonyl and the... 

Aliphatic imidoyl chlorides react faster than the N-alkyl imidoyl chlorides of aromatic carboxylic acids, and arylimidoyl chlorides react the slowest. Electron-withdrawing groups attached to the aryl moieties retard the reaction while electron-donating groups attached to the aryl groups increase the rate of reaction. Likewise, a carbonyl group adjacent to the C=N bond decreases the rate of hydrolysis. Cyclic imidoyl chlorides react rather slowly with water, as evidence by the fact that 2-chloro-A -pyrroline can be recrystallized from aqueous acetone... 

Addition of thiols in basic solution to the C=C—C=0 bond system in a,/3 imsaturated ketones, such as 4-benqrlidene-l-buQrl-pyrrolidine-2,3-dione, has been observed, forming with benzenethiol in piperidine, l-butyl-3-hydroxy-4(a-phenylthiobenzyl)-3-pyrrolin-2-one . Addition of thiols primarily to the C=C bond in C=C—C=0 systems in quinones and lactones has been observed . The reactions were studied in neutral or alkaline solution and probably involve attack by the thiolate anion. In compounds containing both carbonyl or carboxyl groups and acetylenic triple bonds, addition occurs primarily across the acetylene bond. Cyclization of the initial product so formed is also observed . ... 

Azomethine Ylide Precursor. The azide is readily converted into a precursor of azomethine ylides (eq 3). Reactions of the ylides with carbon-carbon multiple bonds and carbonyl group are used in a synthesis of pyrroline and oxazole derivatives (eq 4). ... 

Scheme 41.23 3-Pyrroline-1-carbonyl protecting group by Ishihara et al.

R) -a-pyrrolidinyl tetrazole 1119 pyrroline-1-carbonyl group 1249 pyrrolo-indole core 1104 -tricyclic 1104 pyrroloindoline 750... 

A related type b cyanoamidation leading to 3-pyrrohn-2-ones was reported by the Takemoto group (Scheme 19 20060L2711). Treatment of the alkyne 116 with catalytic Pd(PPh3)4 in xylene gives an equal mixture of 3-pyrrolin-2-one 117 and alkyhdene lactam 118. The mechanism presumably involves a 5-cxo-trig oxidative addition of cyanide and the amide carbonyl across the alkyne isomerization of 118 under the reaction conditions then leads to the formation 117. 

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