Polycyclic heterocycles, reviews

Finally, aromatic nucleophilic denitrocyclization reactions are reviewed for the first time by Stanislav Radi (Prague, Czech Republic). The nitro functionality is a good leaving group, especially for intramolecular reactions, and many such reactions lead to polycyclic heterocyclic ring systems. Frequently, these transformations are a method of choice for preparative purposes. 

Novel polycyclic heterocyclic systems including the isoxazoline ring were described. Thus, oximes 191 and 193 in the presence of sodium hypochlorite afforded heterocycles 192 or 194, respectively (equations 83 and 84). Intramolecular cycloaddition of nitrile oxide was used in the synthesis of the A-ring fragments of la,25-dihydrovitamin D3 and taxane diterpenoids, sulphur-containing isoxazoles, fluoro-substituted aminocyclopentanols and aminocyclopentitols . New gem- and vic-disubstituted effects in such cyclization reactions have been reviewed by Jung. ... 

Since the publication of CHEC-II(1996) <1996CHEC-II(6)1>, in which thermally induced [4+2] cycloadditions have been reviewed, significant progress has been realized in this strategy, especially for the synthesis of polycyclic heterocycles. Cyclophanes 12 containing pyridazine and indole units were used for the synthesis of pentacyclic compounds 13 via a thermally induced transannular inverse-electron-demand Diels-Alder reaction (Equation 2) <20020L127, 2002AGE3261>. 

Topics of relevance to the content of this chapter which have been reviewed during the year include photoactive [2]rotaxanes and [2]catenanes, photochemical synthesis of macrocycles, phototransformations of phthalimido amino acids, photoaddition reactions of amines with aryl alkenes and arenes, photoreactions between arenenitriles and benzylic donors, photostability of drugs, polycyclic heterocycles from aryl- and heteroaryl-2-propenoic acids, photoreactions of pyrroles, photoamination reactions in heterocyclic synthesis, switching of chirality by light, photochromic diarylethenes for molecular photoionics and solid state bimolecular photoreactions. 

Thiadiazole 5-oxides and 5,5-dioxides are the least studied among the four possible isomers of thiadiazole system. The main summary is in the first and the second editions of Comprehensive Heterocyclic Chemistry (84CHEC-I(6)447, 96CHEC-II(4)289). Apparently the 5-oxide and the 5,5-dioxide derivatives have not yet been reviewed. There are very few papers in the literature treating these derivatives, and most of these are regarding polycyclic systems. 

Heterocyclic compounds carrying hydroxyl groups may be compared with phenols. Thomson has reviewed the tautomeric behavior of phenols often both tautomeric forms of polycyclic compounds such as naphthols can be isolated. Early work on hydroxy-thiophenes and -furans was also reviewed by Thomsond but until recently their chemistry has been in a somewhat confused state. A pattern is now beginning to emerge, at least for the a-substituted compounds, which appear to exist as A -oxo derivatives and to attain equilibrium slowly with the corresponding A -oxo forms. For the a-hydroxy compounds, the equilibrium generally favors the A -oxo form. 

It is now evident that it is desirable to divide five-membered meso-ionic heterocycles into two general classes type A and type B. This review is mainly concerned with the presently known 44 members of type A (Table I) and eight members of type B (Table II). Brief reference is made at the end of the review to various six-membered heterocycles and polycyclic systems that have been described as meso-ionic, but it is now firmly proposed that this practice should be discontinued. 

Emphasis is placed on simply substituted free bases. The problems of conformational equilibria in /V-alkylpiperidinium salts and N-quaternization reactions and the relationships of these to conformational equilibria in the free bases are not covered, since this area is a large one requiring separate treatment. In other relevant previous reviews, the topics include heterocyclic conformational analysis,3-7 interactions in azacyclic systems,8 the conformational analysis of piperidine,9 hexahydropyrimidines,10,11 hexahydropyri-dazines,12 quinolizidines,13 the conformational analysis of bi- and polycyclic... 

Although the chemistry of the polycyclic nitrogen heterocycles containing one heteronitrogen atom has been the subject of many comprehensive reviews in recent years, the chemistry of pyrindines has received no such attention.la-lb This review will systematically survey the chemical literature, through 1969, concerning the chemistry of the derivatives of 1-pyrindine (l)-(9), 6,7-dihydro-5//-l-pyrindine (10), hydroxy- and oxo-6,7-dihydro-5//-l-pyrindine, 5/7-l-pyrindine-5,7(6/7)-dione (11), and hexahydro- and octahydro-1-pyrindine. Some medically important 1 -pyrindine derivatives, such as the octahydro- and decahy-drobenzo[a]cyclopenta[/]quinolizines (12) and (13) will also be discussed. 

This review covers nonannelated and annelated eight-membered heterocycles containing one nitrogen. However, it does not include polycyclic structures where nitrogen is the bridgehead atom (1), nor where nonadjacent ring carbons are linked by a bridge (2). 

The use and significance of stereochemical reaction cycles in the reactions of chiral phosphines and phosphonium salts have been surveyed, and a major review of the chemistry of polycyclic C—P heterocycles, much of which is concerned with tertiary phosphines and phosphonium salts, has appeared. Procedures for the synthesis of a range of unidentate and polydentate phosphine ligands have been collected together in a single volume. Aspects of the chemistry of methylphosphines have been included in a review of recent developments in the chemistry of simple P-C compounds. ... 

Xue, W., and Warshawsky, D. (2005). Metabohc activation of polycyclic and heterocyclic aromatic hydrocarbons and DNA damage A review. Toxicol Appl Pharmacol 206, 73-93. 

Two chapters deal with sulfur-containing compounds. The benzisothiazoles and other polycyclic isothiazoles are covered by M. Davis, in a sequel to earlier reviews in Advances in Heterocyclic Chemistry, Volumes 14 and 15. 1,4-Ben-zothiazines and related compounds are dealt with by C. Brown and R. M. Davidson these compounds have not been previously comprehensively reviewed. 

Centropolyindanes constitute a complete family of arylaliphatic polycyclic hydrocarbons containing several indane units. Mutual fusion of the five-membered rings leads to three-dimensional, carbon-rich molecular frameworks bearing a central carbon atom, such as benzo-annelated [3.3.3]propellanes, triquinacenes, and [5.5.5.6]- and [5.5.5.5]fenestranes. In this review, the structural concept of centropolyindanes is contrasted to other fused indane hydrocarbons. Besides the syntheses of the parent centropolyindanes and recently described related indane hydrocarbons, the preparation of a large variety of bridgehead and arene substituted centropolyindanes is presented including strained, heterocyclic, and centrohexacyclic derivatives. In appropriate cases, the particular reactivity and some structural features of these unusual, sterically rigid polycyclic compounds are pointed out. 

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