Hydrozirconation of four-, five-, six- and seven-membered N-alkoxycarbonyl lactams to lactamols

A general, practical, and efficient reduction of four-, five-, six- and, seven-membered N-alkoxycarbonyl lactams to the aldehyde oxidation state is reported. The reduction methodology involves the hydrozirconation reaction by Cp₂Zr(H)Cl under mild conditions and proceeds with very short reaction times and in excellent to good yields. The hydrozirconation of N-alkoxycarbonyl lactams with the Schwartz reagent demonstrated to be the mildest and most general method for the formation of lactamols with a high functional group tolerance.     

Conversion of five-, six-, and seven-membered lactams to racemic or scalemic 2-substituted heterocycles by amidoalkylation

An efficient method for the synthesis of 2-alkyl- and 2-aryl pyrrolidines, piperidines, and azepanes from lactams, in either racemic or enantiopure form, is presented. The lactam nitrogens are acylated with either Boc anhydride or trans-cumylcyclohexyl (TCC) chloroformate. Selective reduction of the lactam carbonyl to the carbinolamide is followed by treatment with benzotriazole. Substitution of the benzotriazole is accomplished by treatment with organometallics, yielding the 2-substituted heterocycles. With TCC, up to 90% diastereoselectivity is achieved. After diastereomer purification, reductive removal of the auxiliary affords enantiopure 2-substituted heterocycles. A mechanistic hypothesis is presented that details the conformational equilibria of the key step.     

Polymerization of five-, six-, and seven-membered ring lactams by using metallic potassium or metallic aluminum alkylate as catalyst and certain N-acyl lactams or diphenyl ketene as initiator

Polymerization of five-, six-, and seven-membered lactams by metallic potassium or MAlEt₄ (where M is Li, Na, or K) as a catalyst and N-acyl lactam or diphenylketene as an initiator was carried out at temperatures below 80°C. By using MAlEt₄ instead of a metallic potassium catalyst in the polymerization of α-piperidone the propagation was continued until the reduced viscosity of polymer reached a value of 0.9. The polymer obtained has a film-forming ability. The experimental results obtained in the gasometry suggest that MAlEt₄ reacts with lactam to form such a complex of the type (where M is Li, Na, or K and X is an ethyl or 2-oxo-alkylene-imine group). The resulting complexes are considered to increase the solubility of catalyst and also to protect the polymer endgroups from side reactions by stabilizing the alkali metal as the complex. In addition, the mode of action of diphenylketene as an initiator was revealed by the facts that the corresponding N-diphenylacetyl lactam was obtained from the reaction of diphenyl ketene with lactam and N-diphenylacetyl lactam itself was useful for the polymerization of α-piperidone.     

Synthesis of unsaturated dibasic acid esters from five-, six-, and seven-membered cycloalkanones

A new route to diesters of symmetrical octene-, decene-, and dodecenedioic acids was proposed. The ratio of the cis/trans-isomers was 1: 4. The synthesis involved oxidative splitting of five-, six-, and seven-membered cycloalkanones with hydrogen peroxide into the corresponding ω-alkenoic acids followed by esterification and metathesis over Re₂O₇/B₂O₃-Al₂O₃-SnMe₄. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1942–1944, November, 2006.     

Thermolysis reaction of 2-acetyl-1-oxo-five-, six-, and seven-membered ring

The rates of gas-phase thermolysis reactions of 2-acetylcyclopentanone 1,2-acetylcyclohexanone 2, N-acetylcaprolactam 3,2-acetylbutyrolactone 4,2-acetyl-2-methylbutyrolactone 5, and 3-acetyl-2-oxazolidinone 6 have been measured over a temperature range of 50 K. They undergo unimolecular first-order elimination reactions for which log A = 11.7, 11.7, 11.2, 11.4, 11.5, and 11.1 s^?1 and E_a = 193.4, 189.5, 153.2, 201.0, 206.8, and 176.1 kJ mol^?1, respectively. The effect of the ring size together with the effect of a heteroatom in the ring on the rate of thermolysis reactions for compound 1–6 is the subject of this work. © 1995 John Wiley & Sons, Inc.     

Regioselective formation of six- and seven-membered ring by intramolecular Pd-catalyzed amination of N-allyl-anthranilamides

A divergent synthesis of quinazolin-4-ones and 1,4-benzodiazepin-5-ones by Pd(II)-catalyzed intramolecular amination of tosylated N-allyl-anthranilamides is described. Both kinds of products were available in high yields depending on the different reaction conditions.     

Synthesis of six- and seven-membered heterocycles under ultrasound irradiation

This review gives an overview of utilization of ultrasound for the synthesis of various heterocyclic compounds. Ultrasonic irradiation has been considered as an efficient methodology in many organic syntheses. With ultrasonic assistance short reaction times, good selectivity and high yields are reported. The use of ultrasound irradiation in organic reactions has been increasing rapidly in recent years.     

Synthesis, crystal structure and antiradical effect of copper(II) Schiff base complexes containing five-, six- and unusual seven-membered rings

The synthesis and solid-state structure of mononuclear copper(II) complexes [Cu(SAIB)(H(2)O)(2)] (1), [Cu(SBAIB)(H(2)O)(2)]·H(2)O (2) and [Cu(SGABA)(H(2)O)(2)] (3) are described. Schiff base ligands H(2)SAIB, H(2)SBAIB and H(2)SGABA chelate the copper(II) ion in an O,N,O tridentate fashion. The square-pyramidal geometry of the final complexes is completed by two water ligands. The formation of an unusual seven-membered ring in the set of copper(II) N-salicylidene-aminoacidates is reported. Compounds 1-3 were evaluated by the antiradical activity assay.     

D-glucosamine trimethylene dithioacetal derivatives: formation of six- and seven-membered ring amino carbasugars. Synthesis of (-)-calystegine B3

By virtue of carefully chosen protecting groups, d-glucosamine trimethylene dithioacetal derivatives were successfully oxidized to the corresponding 6-aldehydes. This methodology reverses the donor and acceptor position on a normal open chain sugar and changes the relative position of the N-substituent. From the 6-aldehydes, heptose epoxide derivatives were prepared by a Corey-Chaykovsky reaction, and cyclized by the Corey-Seebach method. Depending on the designed protecting groups, the orthogonally protected six- and seven-membered ring amino carbasugars can be produced selectively and efficiently. (-)-Calystegine B(3) was synthesized from one of those products with high yield. This is the first anionic cyclization pathway to calystegine type structures.     

Suzuki reaction of vinyl triflates from six- and seven-membered N-alkoxycarbonyl lactams with boronic acids and esters

The Pd(0)-catalyzed reaction of vinyl triflates from N-alkoxycarbonyl lactams with different boron compounds has been studied. The coupling reaction of alkenylboronates and arylboronic acids with six- and seven-membered lactam-derived N-alkoxycarbonyl vinyl triflates was feasible under very mild conditions in THF-water employing (Ph3P)2PdCl2 as a catalyst and Na2CO3 as a base, which provided in high yields the corresponding 6- or 7-substituted N-alkoxycarbonyl-3,4-dihydro-2H-pyridines and N-alkoxycarbonyl-2,3,4,5-tetrahydroazepines. Allylboronates reacted slower but, with vinyl triflates from delta-valerolactam, still gave acceptable yields of the coupling product. Alkylboronic acids required different reaction conditions, in particular the presence of Ag2O together with a base in anhydrous toluene and (dppf)PdCl2 as a catalyst, affording the corresponding 6-alkyl-N-alkoxycarbonyl-3,4-dihydro-2H-pyridines in high yields.     

Synthesis of dispirotetrahydropyran-2,4-diones containing six- and seven-membered rings

Methyl 1-(1-bromocyclohexylcarbonyl)cycloheptane- and 1-(1-bromocycloheptylcarbonyl)cyclohexanecarboxylates react with zinc and aromatic aldehydes yielding 17-aryl-16-oxadispiro[5.1.6.3]heptadecane-7,15-diones and 15-aryl-16-oxadispiro[5.1.6.3]heptadecane-7,17-diones respectively.     

Synthesis and reactions of aminoporphyrazines with annulated five- and seven-membered rings

The novel five- and seven-membered ring appended aminoporphyrazines 3 and 12 have been prepared via mixed Linstead macrocyclization. The structures of both have been unequivocally established by X-ray crystallographic studies. Reductive deselenation of selenadiazole 3 in the presence of 9,10-phenanthrenequinone or 2,3-butanedione results in the formation of pyrazines 6a,b, whereas oxidation of porphyrazine 12 gave the corresponding seco derivative 14. seco-Porphyrazine 14 mediates the generation of singlet oxygen with a quantum yield of 0.74.     

Conformation and stereodynamics of 1,2-diaryltetrahydropyrimidine and of its five- and seven-membered ring analogs

The 1-(2-nitrophenyl)-2-(2-methylphenyl)-1,4,5,6-tetrahydropyrimidine and its five- and seven-membered ring analogs were synthesized and their conformational properties investigated by low temperature NMR spectroscopy and DFT theoretical calculations. Restricted rotation of the aryl substituents were observed in all cases and the corresponding barriers determined. In the case of the six-membered ring derivative the additional conformers resulting from a ring inversion process were also detected.     

Reactivity of alicyclic 1,5,9-triketones toward five-, six-, and seven-membered rings in acidic medium. Stereochemistry of intramolecular cyclization products

Chemistry of Heterocyclic Compounds - Among nine alicyclic 1,5,9-triketones with differently fused 5-, 6-, and 7-membered rings in the molecule, existing as mixtures of 3–6 diastereomers,...     

Reactions of arylhydrazines with α-formyl derivatives of six-and seven-membered ring lactams

Reactions of -formyl derivatives of N-methyl--valerolactam and N-methyl--caprolactam with arylhydrazines lead to the formation of 3,4,5,10-tetrahydroazepino [3, 4-b] indole-1 (2H)-one and 2,3,4,5,6,11-hexahydro-1H-azocino [3,4-b] indol-1-one derivatives. As the size of the lactam ring is increased the role of competing reactions, such as dealkylation at the indole nitrogen atom and the formation of 5-pyrazolone via reaction with -unsubstituted phenylhydrazine, also increases.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1398–1403, October, 1988.     

Diastereoselective synthesis of three-, five-, six-, and seven-membered rings from Fischer carbene complexes and 4-unsubstituted 1-amino-1,3-dienes

Fischer carbene complexes react with 4-unsubstituted 1-amino-1,3-dienes to give different carbocyclization products depending on the nature of the carbene complex and on the substitution pattern of the aminodiene. Thus, the reaction of arylcarbene chromium complexes and 1-aminodienes diastereoselectively affords cyclopropane derivatives by means of a formal [2+1] carbocyclization reaction. In particular, pentacarbonyl[(2-furyl)(methoxy)methylene]chromium complex furnishes formal [4+1] carbocyclization products. Starting from beta-substituted alkenylcarbene complexes, formal [4+1] reactions occur and cyclopentenamine derivatives are diastereoselectively formed. However, when the alpha,beta-disubstituted alkenylcarbene complex pentacarbonyl[(5,6-dihydro-2H-pyran-2-yl)(methoxy)methylene]tungsten is used, the outcome of the reaction depends on the substitution on the carbon atom at the 3-position of the aminodiene, generating the [3+2] or [4+3]-cyclization products if the substituent is or is not a hydrogen atom, respectively. Finally, when the reaction is performed with alkynylcarbene complexes, benzaldehyde derivatives are obtained if the triple-bond substituent is a phenyl group or indene derivatives if the group is an alkenyl moiety.     

Synthesis of unsaturated seven-membered ring lactams through palladium-catalyzed amination and intramolecular cyclocarbonylation reactions of amines and Baylis-Hillman acetates

A versatile synthesis of unsaturated seven-membered ring lactams has been developed. The sequence involves hydroamination of Baylis-Hillman acetate with amines, followed by intramolecular cyclocarbonylation reactions of the resulting allylamines. This process can tolerate a wide array of functional groups, and affords lactams in excellent yields.     

Biomimetic aerobic oxidation of amino alcohols to lactams

The right path: N-Protected amino alcohols undergo aerobic and biomimetic oxidation to the corresponding lactams in the presence of a ruthenium catalyst and a combination of electron-transfer mediators under air. The reaction was used for the synthesis of five-, six-, and seven-, membered lactams and showed good tolerance to a number of N-protecting groups.     

Chiral-optical properties of six- and seven-membered benzothioamides

The chiral-optical properties of R-(+)-4-methyl-3,4-di-hydroisoquinoline-1-thione and R-(-)-3-methyl-, R-(+)-4-methyl-, and S-(+)-5-methyl-2,3,4,5-tetrahydrobenz[c]-azepine-1-thiones were studied. A significant increase in the intensities of the Cotton effects (CE), particularly for the CE due to the n * transition in the benzothioamide chromophore, is observed on passing from six-membered to seven-membered benzothiolactams with the same orientation of the asymmetric center relative to the chromophore. The signs of the CE due to the n * transition in the benzothioamide chromophore and the ^* transition in the aromatic chromophore at 250–280 nm (the ¹Lb band) correlate with the type of conformation of the thiolactam ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1233–1237, September, 1985.