Exocyclic ester group

Cyclic phosphates polymerize by both cationic and anionic mechanisms. Anionic polymerization is the method of choice for preparation of high molecular weight polymers because in cationic polymerization the reaction of exocyclic ester group leads to chain transfer ... 

The addition of diazomethane to cylohexene is so slow and low yielding that such additions only provide a practicable entry to the bicyclo[4.1. OJheptane series if the double bond is activated in some way for example, by conjugation. Hence diazomethane readily underwent addition to cyclohexa-1,3-diene to give 7,8-diazabicyclo[4.3.0]nona-4,7-diene (18 h, 73%), which on thermolysis (110-180 C), photolysis, or sensitized photolysis gave an essentially quantitative yield of bicyclo[4.1.0]hept-2-ene. Cyclohexenes in which the double bond is activated by one ° or exocyclic ester groups or by a carbonyl group in the ring (cyclohexen-... 

When malonate 9 is treated with polyphosphoric acid at room temperature, formation of lactone 11 is observed, similar to the Darzens procedure with the use of sulfuric acid. The structure of lactone is being retained during subsequent hydrolysis and decarboxylation of the exocyclic ester group followed up treatment with anhydrous hydrogen fluoride gives dimethyl tetrahydronaphthalene carboxylic acid 12. Hydrolysis and decarboxylation of 10 under standard conditions gives the same product 12. ... 

We also performed a single-crystal X-ray structure analysis of this lead compound. The solid state structure of this compound depicted in Fig. 3-15 shows a half-boat-like ( sofa ) conformation with the 9-phenanthryl group in a quasi-axial or r/Mf/.v/-flagpole position, and the a, 3-unsaturated exocyclic ester in a s-cis conformation. This cleft-like conformation is advantageous for the creation of centers with a high recognition ability, since one enantiomer fits in better than the other thus leading to selectivity. 

A formal pathway is shown in Scheme 5 for an endocyclic system, as was shown in Scheme 2 for an exocyclic pathway. The obvious difference is that, after the formation of the monoanion of the hydrate and the intramolecular attack, the next step in Scheme 5 involves fission to give separate species containing the hydrolysed ester group and the catalytic moiety... 

Chen and co-authors in their work [50] offered key stages for mechanism of heterocyclization leading to compounds 25 and 26 (Scheme 12). The reaction sequence for azolopyrimidines 25 formation is very similar to that published in [47] and presented in Scheme 9. Pathway to tetrahydroderivatives 26, in opinion of [50], also includes at the beginning Knoeveganel condensation. Further step of the reaction in this case should be the addition of exocyclic NH2 group of aminoazole to enone fragment of unsaturated ester, with subsequent cyclization of the adduct formed into final tetrahydropyrimidine (Scheme 14). 

In the case of X = C (CN)2 two nonequivalent CN groups are observed. Similarly, two nonequivalent ester groups are observed with X = C (COOEt)2 suggesting that the exocyclic group bond has double bond character <93MRC447> (see <76JCS(P1)744 . With X = C (CN)(COOEt) only one isomer was observed even at 373 K but it could not be identified <93MRC447>. 

The cyanobromide (371) was condensed with the bc portion (347) to give the thioether (372) sulfide contraction to give (373) was accomplished using tris(/3-cyanoethyl) phosphine, and with phosphorus pentasulfide the thiolactam-thiolactone (374) was produced. After treatment with Meerwein s salt, reaction with dimethylamine opened the lactone with concomitant formation of an exocyclic methylene group, and subsequent treatment with cobalt chloride or iodide gave the chelate (375) which was reacted with diazabicyclononane to give bisnorcobyrinic add [Pg.435]

In rather unreliable reactions, pyridine and its 3-methyl and 3,5-dimethyl derivatives with MP and 1 mole of methanol yield 2-methoxy-1,2-dihydropyridines (e.g., 122).292 This contrasts with DMAD which yields indolizines (e.g., 35 and 36), perhaps because the extra ester group encourages the methoxide ion to add to the exocyclic double bond, but 4-methylpyridine with MP gives the same products (see earlier) as obtained in the absence of added methanol.292 Replacing the methanol by water gave compounds exemplified by 123, where the 5 6 -double... 

Gibberellin A5 (C H Os) has a melting point of 260-61° and forms a methyl ester (m.p. 190-91°). The infrared spectra of Nujol mulls of the acid and ester (see Table II) show the presence of alcoholic hydroxyl, hydroxyl of carboxylic acid, unconjugated five-ring lactone, carboxyl (or ester) carbonyl, exocyclic methylene group, and a cis-disubstituted double bond. Catalytic hydrogenation of the methyl ester confirmed the presence of two double bonds. 

When the propargyl phosphate 225 was heated in the presence of Pd2(DBA)3-CHCl3 and sodium acetate in THF, the central sp carbon atom of the (j-allenylpalladium complex, formed from the propargyl alcohol ester and Pd(0), was attacked by the lactam nitrogen atom to yield the carbapenam 226 with an exocyclic methylene group <2001TL4869>. 

The enaminoketone structure of compound 220 in the crystal state was derived from the IR spectrum which contained the following absorption bands 1760 (ester carbonyl), 1640 (exocyclic carbonyl group), 1630 (lactone carbonyl in the pyran ring), and 3350 cm (strongly broadened z(N-H) band) <2001RJ01318>. 

The cyclopropyl group is often equivalent to the vinyl group (-CH=CH2) thus the exocyclic bond length in 1 is abnormally short and not far from the C-R bond length found in CH2=CH-R (R = vinyl, carbonyl, acid and ester groups). 

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