Polycyclic Heterocycles Research Articles

NEW 6-(3-INDOLYL)BENZO[B]CARBAZOLES

Some attempts have been carried out to synthesize polycyclic heterocyclic compounds derived from new benzocarbazoles (1) . New 6-(3-indolyl)benzo[ b ]-carbazoles ( 2a ) have been synthesised in good yields from the reaction of simple indoles and o -phthaldialdehid in methanol catalysed by p -toulenesulfonic acid monohydrate. Their precise structure were established by microanalysis, spectroscopy, and X-ray crystallography of the benzo[ b ]carbazole (2a) . Keywords: indoles, polycyclic heterocyclic compounds, benzo[ b ]carbazoles

Diastereoselective Synthesis of Chiral cis‐Annulated Polycyclic Heterocycles from D‐Glucose by Domino Knoevenagel—Hetero‐Diels—Alder Reaction.

A new and simple chiral synthesis of cis-annulated polycyclic dihydropyrans 4 and 8 has been achieved by domino Knoevenagel-hetero-Diels-Alder reactions of O-prenyl derivative of the chiral sugar derived aldehyde 2 with 1,3-dicarbonyl compounds 1 or 6 in MeCN in the presence of a catalytic amount of ethylenedi-ammonium diacetate (EDDA) The products are formed with extremely high cis-selectivity in good to excellent yields.

COMPARATIVE METABOLISM OF PHENANTHRO[3,4-B]THIOPHENE, PHENANTHRO[4,3-B]THIOPHENE AND THEIR CARBON ANALOG BENZO[C]PHENANTHRENE BY RAT LIVER MICROSOMES

Phenanthro[3,4-b]thiophene (P[3,4-b]T) and phenanthro[4,3-b]thiophene (P[4,3-b]T) are thiasters of weakly mutagenic benzo[c]phenanthrene (B[c]P). These polycyclic sulfur heterocycles (thia-PAHs) represent a group of chemicals which have been identified in cigarette smoke. P[3,4-b]T is a potent mutagen in Salmonella typhimurium strain TA100 in the presence of rat liver S9, whereas its isosteric isomer P[4,3-b]T is a nonmutagenic compound. In order to understand the mechanism underlying the differences in the mutagenic activity of P[3,4-b]T and P[4,3-b]T, we have investigated the metabolism of P[3,4-b]T, P[4,3-b]T, and their carbon analogue B[c]P by rat liver microsomes. The liver microsomes from rats treated with Aroclor 1254 metabolized P[3,4-b]T, P[3,4-b]T, and B[c]P at a rate nearly 7- to 9-fold greater than of the control liver microsomes. High-performance liquid chromatography (HPLC) analysis of the metabolites formed showed that B[c]P was metabolized almost exclusively to its dihydrodiols which comprised predominantly K-region diol as noted in the previous studies. Our preliminary studies on the metabolism of P[3,4-b]T, P[4,3-b]T and B[c]P by liver microsomes from control and Aroclor 1254-treated rats have shown a significant reduction in the formation of 6,7-diol (K-region diol) and 8,9-diol (diol with a bay-region double bond) of the two thia-PAHs compared to the formation of analogous 5,6-diol (K-region diol) and 3,4-diol (diol with a bay-region double bond) from B[c]P. Both P[3,4-b]T and P[4,3b]T produced a major, relatively nonpolar metabolite(s) (80–96% of total metabolites). These studies indicate that the highly mutagenic P[3,4-b]T is not metabolized to dihydrodiol with a bay-region double bond to any greater extent than the weakly or nonmutagenic B[c]P or P[4,3-b]T, suggesting that the metabolite(s) other than P[3,4-b]T8,9-diol is likely to be involved in the mutagenicity of P[3,4-b]T.

A Novel Approach to Heterocycles via Photocycloaddition Reactions of Nitrogen‐Containing Heteroaromatics

AbstractFor Abstract see ChemInform Abstract in Full Text.

ChemInform Abstract: Iodine(V) Reagents in Organic Synthesis. Part 1. Synthesis of Polycyclic Heterocycles via Dess—Martin Periodinane Mediated Cascade Cyclization: Generality, Scope, and Mechanism of the Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enyne Metathesis of Norbornene Derivatives: A Facile Approach to Polycyclic Heterocycles

Norbornene derivatives bearing propargyloxy substituents in the 5- and 6-positions undergo a cascade series of enyne metatheses when treated with Grubbs' catalyst and a terminal alkene, leading to heterocyclic dienes which undergo a stereoselective DielsAlder reaction, giving access to a range of polycyclic heterocycles. The process is compatible with both terminal and internal alkynes, and depending upon the structure of the alkene can give symmetrical or unsymmetrical products. Mechanistic studies have shown that the initial metathesis reaction is between the strained norbornene and Grubbs' catalyst, rather than between the alkyne and Grubbs' catalyst.

ChemInform Abstract: Polycyclic Heterocycles with Acidic N—H Group. Part 2. Synthesis of Some Isomeric Quinoxaline Derivatives with 6‐Azauracil Cycle

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Iodine(V) reagents in organic synthesis. Part 1. Synthesis of polycyclic heterocycles via Dess-Martin periodinane-mediated cascade cyclization: generality, scope, and mechanism of the reaction.

The scope, generality, and mechanism of the Dess-Martin periodinane-mediated cyclization reaction of unsaturated anilides discovered during the total synthesis of the CP-molecules (phomoidrides A and B) are delineated. A plethora of heterocyclic compounds are accessible by employing gamma,delta-unsaturated amides (derived from anilines and carboxylic acids), urethanes, or ureas (derived from isocyanates and allylic alcohols and amines) as substrates. Optimization of the reaction led to room-temperature conditions, while isotope labeling studies allowed a mechanistic rationale for this cascade reaction.

Asymmetric aza-Diels–Alder reactions of indole 2-carboxaldehydes

The aza-Diels–Alder reaction of substituted indole 2-carboxaldehydes with Danishefsky's diene has been investigated. The reaction proceeds with a high degree of diastereoselectivity providing highly functionalized 2-(2-piperidyl)indoles which are further elaborated into novel polycyclic heterocycles.

含窒素芳香族化合物の光環化付加反応による複素環合成

Photochemistry of aromatic compounds has received much attention from both the mechanistic and synthetic perspectives, and the intra- and intermolecular photochemical cycloaddition of carbon aromatics is well documented. Furthermore, the photocycloaddition of alkenes to benzene derivatives is also a useful method for synthesizing natural products. However, in contrast, the photocycloaddition reaction of aza-aromatics, such as pyridines, pyridazines, pyrazines, or pyrimidines, is an underdeveloped area of research. We found that the induction of suitable substituents to appropriate position of aza-aromatic ring made the photoreactivity considerably high. Many new photochemical reactions for pyridine derivatives have been found in photodimerization, photocycloaddition with alkenes, furan, benzofuran or cyanonaphthalene. These reactions provide not only new photochemical aspect of aza-aromatics, but also useful synthetic method of polycyclic heterocycles.

Diastereoselective intramolecular hetero Diels–Alder approach towards polycyclic heterocycles

Several different heterocyclic aldehydes, derived from pyrazole, pyrimidine, pyridine, indole and thiazole, were converted to polyheterocyclic compounds containing four to seven rings. The key steps in the sequence were a Knoevenagel condensation of the aldehyde and a heterocyclic carbonyl compound, such as pyrazolone and isoxazolone, followed by an intramolecular hetero Diels–Alder reaction. Most final products were isolated with high yield and diastereoselecivity. The isoxazolo fused cycloadducts formed interesting spiro-adducts upon heating. The cis nature of the bridging hydrogens of the heterocycles was evidenced by X-ray diffraction analysis. † † Crystallographic data (excluding structure factors) ending pages for the structures in this paper, have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication numbers CCDC 169436, CCDC 169437 and CCDC 169438. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44(0)-1223-336033 or e-mail: deposit@ccdc.cam.ac.uk).

Sequential oxopyridinium betaine cycloaddition–palladium catalysed cyclisation–anion capture processes

Katritzky's oxopyridinium betaine cycloaddition is employed to generate bridged bicyclic substrates suitable for our palladium(0) catalysed cyclisation–anion capture methodology. A variety of polycyclic heterocycles have been synthesised via monocyclisation–organotin(IV) capture with or without incorporation of carbon monoxide. Sequential cycloaddition–cyclisation can be performed as a one pot process to deliver substantial gain in molecular complexity.

Synthesis of some new thiazolo[3,2- a]pyridines and related heterocyclic systems

New 2,7-disubstituted 5-amino-6,8-dicyano-2,3-dihydro-3-oxo thiazolo[3,2- a]pyridines have been prepared. Their cyclization with formamide, nitrous acid and triethylorthoformate afforded a series of polycyclic heterocycles containing condensed pyrimidine and triazine rings. Antifungal tests were also performed.

The Preparation of Certain Nitrogen and Sulfur Containing Polycyclic Heterocycles by the Reaction of Arynes Possessing Charged Groups with a-Lithio-a-cyano-o-tolunitrile and a-Lithio-3-thienylacetonitrile

The Preparation of Certain Nitrogen and Sulfur Containing Polycyclic Heterocycles by the Reaction of Arynes Possessing Charged Groups with a-Lithio-a-cyano-o-tolunitrile and a-Lithio-3-thienylacetonitrile

B-Halovinylaldehydes - As Versatile Reactive Intermediates in the Syntheses of Condensed Fused Ring Polycyclic Heterocycles

b-Halovinylaldehydes - As Versatile Reactive Intermediates in the Syntheses of Condensed Fused Ring Polycyclic Heterocycles

Substrate influence on the frying process.

The substrate affects frying oil in different ways during the frying. Water is released from the substrate, which is converted into steam and participates in hydrolytical processes of frying fats. The transfer of fat into the substrate and from the substrate into frying fat depends on the fat content in the substrate and on the frying conditions. Other, more polar substances than triacylglycerols, including pigments and their precursors, pass in frying oil. Oxidation processes in frying oil are inhibited by the substrate, especially by proteins, starch or phenolic substances. Mutagenic polycyclic aromatic heterocycles are produced during the interaction of frying fat and protein. Oxidation products are bound to proteins and other components of the substrate. Flavour substances are produced by reactions of oxidized frying oil with proteins and other sulphur and nitrogen substances in the substrate.

Photocyclization of aryl‐ and heteroaryl‐2‐propenoic acid derivatives. Synthesis of polycyclic heterocycles

Photocyclization of aryl‐ and heteroaryl‐2‐propenoic acid derivatives. Synthesis of polycyclic heterocycles

Facile Synthesis of Polycyclic pyridines, Bipyridines, and Oligopyridines

AbstractThe preparation of polycyclic heterocycles with one or more nitrogen atoms and different binding angles by a domino reaction is described. These compounds (4–6, 8a–b) are formed by the reaction of β‐amino ketone hydrochlorides 1 or 2 (Mannich bases) with ketones 3. Especially the synthesis of the terpyridines 8a and 8b in a double domino reaction is very useful (yield 70 and 59%) and opens a route to torands.

Regio- and stereoselective intramolecular Heck reactions of N-acyl-2,3-dihydro-4-pyridones

Intramolecular Heck reactions of N-acyl-2,3-dihydro-4-pyridones provide polycyclic heterocycles with high regio- and stereoselectivity.

Synthesis of Polycyclic Nitrogen-containing Heterocycles: One Pot Formation of 1,6-Naphthyridine Ring System by Reaction of Amino-cycano-methylyhio-heterocycles with Dialkyl Acetylenedicarboxylates

Synthesis of Polycyclic Nitrogen-containing Heterocycles: One Pot Formation of 1,6-Naphthyridine Ring System by Reaction of Amino-cycano-methylyhio-heterocycles with Dialkyl Acetylenedicarboxylates