Pyridines cyclopenta

Mention must first be made of some interesting compounds in which the OsHs" ion is bonded to nitrogen these are pyridine cyclopenta-dienylide 126) and diazocyclopentadiene 28). Triphenylphosphonium... 

A final example of this synthetic methodology is the chiral synthesis of the cyclopenta[c]pyridine ring system of (-)-plectrodorine 43. Oxazole 41 was heated in o-... 

The reaction of 3-aminocyclopenta[c]pyridine and EMME at 150°C for 2 hr afforded cyclopenta[g]pyrido[l,2-a]pyrimidine-3-carboxylate (1064, R = H) in 54% yield (84KFZ931). 

With the aid of a Knoevenagel condensation and a Staudinger reaction, 2-azidocyclopent-l-ene 1-carbaldehydes (195) can be converted into suitable products for a cyclopenta[b]pyridine synthesis [89JCS(P1)1369], as shown in Scheme 72. In order to bring the ester carbonyl function and the imino-phosphorane group into close proximity suitable for cyclization reactions, the 1,3-diene system 196 should possess the s-cis conformation. Furthermore, the exocyclic double bond should show a cis conformation. To achieve... 

As shown in Scheme 73, a substituent a to the carbonyl group hampers the formation of the cyclopenta[h]pyridines, as the s-cis conformation of 197 is sterically unfavorable. This limits the synthesis to 3-unsubstituted derivatives 198 only [89JCS(P1)1369]. 

Schomaker, V., and L. Pauling The electron diffraction investigation of the structure of benzene, pyridine, pyrazine, butadiene-1,3, cyclopenta-diene, furan, p5rrrole, and thiophene. J. Amer. chem. Soc. 61,1769 (1939). 

A reactor was charged with methyl 6-hydroxy-2-oxohexahydro-3,5-methano-2H-cyclopenta-[b]furan-7-carboxylate (25.0 g) and 2-chloroacetic acid chloride (16.0 g) dissolved in 180 ml of THF and then cooled to below 20°C and treated with the drop-wise addition of pyridine (10.7 g). The solution was stirred at ambient temperature for 1 hour and then combined with 5% aqueous solution of sodium hydrogen carbonate (40 g). Following an ordinary posttreatment workup, 31.5 g of product were isolated after recrystallization from isopropyl ether. 

We illustrate this by two examples. Reaction of the 6-phenyl-1,2,4-triazine (407) with the enamine (406) follows orientation A since secondary orbital interactions between the n-electrons of the amino group and the 77-electrons of the phenyl ring are possible. The dihydropyridine (408) can eliminate the amine to form the cyclopenta[c]pyridine (409) since the cis orientated proton at C-3 can shift to the nitrogen to form the 1,4-dihy-dropyridine (410) from which the amine is eliminated. 

The dominant influence of secondary orbital interactions is observed in the reaction of the cyclopenta[e][l,2,4]triazine ester (415) witl the two enamines (416) and (417). In the first case the fused pyridine (418) was obtained directly in the latter the dihydropyridine (419) was isolated, and aromatized, by iV-oxidation and Cope elimination, to (420) <82CB2807>. 

One approach to tetrahydropyridinones is the Lewis acid mediated hetero-Diels-Alder reaction of electron-rich dienes with polystyrene-bound imines (Entries 3 and 4, Table 15.23). The Ugi reaction of 5-oxo carboxylic acids and primary amines with support-bound isonitriles has been used to prepare piperidinones on insoluble supports (Entry 5, Table 15.23). Entry 6 in Table 15.23 is an example of the preparation of a 4-piperidinone by amine-induced 3-elimination of a resin-bound sulfinate followed by Michael addition of the amine to the newly generated divinyl ketone. The intramolecular Pauson-Khand reaction of propargyl(3-butenyl)amines, which yields cyclopenta[c]pyridin-6-ones, is depicted in Table 12.4. 

The mass spectra of benzofused pseudoazulenes 65 and 80 -83 show the mass ion as the base peak, and intense peaks are observed that correspond to the doubly charged molecular ion. The authors197 have attributed this fact to the aromaticity of these systems. This conclusion, however, cannot be drawn for all pseudoazulenes since the relative intensity of the mass ion for 26b is only 5.5%,55 for 4-methyl-4H-cyclopenta[b]quinoline 64%, 14 for 5-methyl-5/f-cyclopenta[c]quinoline7.0%,123andfor2-phenacyl-9-benzoyl-2H-indeno[2,1-fo] pyridine 18%.105... 

Dihydroanisoles, m61, m62 6,7-Dihydro-5//-cyclopenta[b]pyridine, c360 10,1 l-Dihydro-5//-dibenz[fr/]acepine, il2 2,5-Dihydro-2,5-dimethoxyfuran, d436... 

To a solution of 1.14 g of 3-methyl-trans-4a-cisoid-4a,5a-cis-5a-l,4a,5,5a,10b,10c-hexahydro-7-dioxino[5,4-a]cyclopenta[b]benzofuranyl-methanol in 10 ml of dimethoxyethane cooled in an ice bath was added 0.43 ml of anhydrous pyridine and 0.38 ml ofthionyl chloride, and the mixture was stirred for 3 hours at room temperature. After addition of ether to the reaction mixture, the precipitate was filtered, and water was added to the filtrate and the mixture was extracted three times with ether. The extract was washed with aqueous saturated solution of copper sulfate, water, aqueous saturated solution of sodium hydrogen carbonate and aqueous saturated solution of sodium chloride, dried, and concentrated to give 1.2 g of crude crystals. The crude crystals were recrystallized from ethyl acetate-hexane to yield 1 g of the pure titled chloride (m.p. 94-95°C, yield 83%). 

To a solution of 350 mg of methyl 4-[2-endo-hydroxy-l-exo-hydroxymethyl-3a,8b-cis-2,3,3a,8b-tetrahydro-lH-5-cyclopenta[b]benzofranyl]butyrate in 3.5 ml of anhydrous dimethylformamide cooled in an ice bath were added 140 mg of imidazole and 360 mg of t-butyldimethylsilyl chloride, and after the mixture was stirred for 3 hours at room temperature, dimethylformamide was removed under reduced pressure. The residue was dissolved in a mixture of 10 ml of acetic anhydride and 5 ml of pyridine. After the mixture was stirred for 2 hours at room temperature, the reaction mixture was concentrated. 

Lithium salt of cyclopenta[6]pyridinyl with [( 5-Cp )ZrCl2] gives the 5-complex 12 (02JCS(D)2995). Cyclopenta[Z ]pyridine with [Zr(NMe2)4] gives 13 in the presence of dimethylamine. 

Hexahydro-3-(hydroxymethyl)-8a-methyl-2-phenyl[2S,3S,8aR]-5-oxo-5H-oxazolo-[3,2-a]pyridine 5H-Oxazolo[3,2-a]pyridin-5-one, hexahydro-3-(hydroxymethyl)-8a-methyl-2-phenyl-, (2S-(2a,3p,8ap)]- (116950-01-7), 69, 55 3,3A,3B,4,6A,7A-HEXAHYDRO-3,4,7-METHENO-7H-CYCLOPENTA[A]PENTALENE-DICARBOXYLIC ACID 3,4,7-Metheno-7H-cyclopenta[a]pentalene-7,8-dicarboxylic acid, 3,3a,3b,4,6a,7a-hexahydro- (61206-25-5), 68,198 HEXAHYDRO-4,4,7-TRIMETHYL-4H-1,3-BENZOXATHIIN 4H-1,3-BENZOXATHIIN, HEXAHYDRO-4,4,7-TRIMETHYL- (59324-06-0), 65, 215 Hexamethylphosphoric triamide (HMPA) (680-31-9), 66, 44, 45, 51, 88, 94 69, 48, 49 Hexanal (66-25-1), 69, 107... 

Bis(l,l-dicyanopent-4-ynyl)pyrazine (241) gave a separable mixture of 3-(l,l-dicyanopcnt-4-ynyl)-5,6-dihydro-7//-cyclopcnta b pyridine-7,7-dicarbonitrilc (242) and 3-( 1,1 -dicyanopent-4-ynyl)-5,6-dihydro-7//-cyclopenta[c]pyridine-... 

Cyclopenta[c]pyridin-7-one, 5,6-dihydro-3-methyl-1-propyl-, 57, 22 Cyclopenta-pyridines, see also Pyrindines Cyclopenta[h]pyrrole, 6-hydroximino-octahydro-1-methyl, 58, 22 Cyclopenta[h]selenopyran, 2,4a,5,6,7,7a-hexahydro-2-methyl-, synth, 55, 17 Cyclopenta[c]thiopyran, protonation, 60, 119... 

Cyclopenta-fused pyridines 48 have been synthesized through a cascade initiated by intermolecular addition of C radicals to the C = N triple bond in vinylisonitriles. The reaction in Scheme 2.8 shows addition of the nucleophilic alkynyl radical 49 to the carbon end of the isonitrile group in 46 to give vinyl radical 50, which undergoes a... 

REDUCTION, REAGENTS Bis(triphenyl-phosphine)copper tetrahydroborate. Borane-Pyridine. Calcium-Methylamine/ ethylenediaminc. Chlorobis(cyclopenta-dienyl)tetrahydroboratozirconium(IV). Chromium(II)-Amine complexes. Copper(0)-lsonitrile complexes. 2,2-Dihydroxy-l, 1-binaphthyl-Lithium aluminum hydride. Di-iododimethylsilane. Diisobutyl-aluminum 2,6-di-/-butylphenoxide. Diisobutyl aluminum hydride. Dimethyl sulfide-Trifluoroacetic anhydride. Disodium tetracarbonylferrate. Lithium-Ammonia. Lithium-Ethylenediamine. Lithium bronze. Lithium aluminum hydride. Lithium triethylborohydride. Potassium-Graphite. 1,3-Propanedithiol. Pyridine-Sulfur trioxide complex. 

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