Oxygen heterocycles, reviews

In 1999, Bob Atkinson wrote [1] that aziridination reactions were epoxida-tion s poor relation , and this was undoubtedly true at that time the scope of the synthetic methods available for preparation of aziridines was rather narrow when compared to the diversity of the procedures used for the preparation of the analogous oxygenated heterocycles. The preparation of aziridines has formed the basis of several reviews [2] and the reader is directed towards those works for a comprehensive analysis of the area this chapter presents a concise overview of classical methods and focuses on modern advances in the area of aziridine synthesis, with particular attention to stereoselective reactions between nitrenes and al-kenes on the one hand, and carbenes and imines on the other. 

Reviews of saturated oxygen heterocycles <00JCS(P1)1291>, routes to 2,2-dimethyl-2H-[l]benzopyrans <00H(53)1193> and pyranonaphthoquinone antibiotics <00T1937>, HIV-1 active Calophyllum coumarins <00H(53)453> and of the application of (3-halovinylaldehydes in heterocyclic synthesis <00H(53)941> have appeared. 

Reviews of thietanes <99MI138> and saturated oxygen heterocycles including oxetanes are available <98JCS(P1)4175>. 

Unsaturated Oxygen Heterocyclic Molecules , F. M. Dean, in MTP International Review of Science, Organic Chemistry Series Two , ed. D. H. Hey, Butterworth, London, 1975, vol. 4, pp. 209-250. 

The advent of the polyether antibiotics with the challenging aspect of stereocontrolled construction of the substituted tetrahydrofuran units has greatly extended the chemistry of this oxygen heterocycle. The nonactins (194), lasalocid A (195) and monensin (196) are among the ionophores for which syntheses have been achieved. Detailed reviews on synthesis of reduced furans are available (65HOU(6/3)l, 80H(14)1825). 

A number of review articles deal with electron impact mass spectra of oxygen heterocycles (69BSF4545, B-71MS139, B-74MI22202), but little use appears to have been made of techniques such as chemical ionization or negative ion spectrometry. 

There is a considerable amount of information on the conformation of six-membered oxygen heterocycles and several texts include useful reviews (B-71MI22200, B-77SH(2)78, B-80MI22203). 

The application of polyketone-derived anions to the synthesis of oxygen heterocycles has much to offer a comprehensive review of this area has been published (77T2159). 

The photolysis of cyclic ketones, in general, results in homolytic cleavage of the carbon-carbon bond adjacent to the carbonyl function. For details of this process, the reader is referred to the review by Srinivasan.425 Included among the photoproducts are certain oxygen heterocycles, formed by cyclization of reactive intermediates. Thus, cleavage in a cyclic /3-diketone, such as tetramethylcyclobutane-1,3-dione or hexamethylcyclohexane-l,3,5-trione [Eq. (110)] is followed by cyclization on the oxygen atom to form a lactone.426,427 y-Lactone formation is also observed on photolysis of 2,2-diphenylindane-l,3-dione [Eq. (Ill)] in ether, and the process is reversible.428... 

Naturally Occurring Furan Derivatives The mass spectra of naturally occurring oxygen heterocyclics were reviewed only recently.52... 

During these five decades, the rearrangement has also evoked much interest in its extensions into the nitrogen and oxygen heterocyclic systems. The present review is an attempt to present some of the chemistry relating to nitrogen heterocyclic compounds wherein the... 

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