O-heterocyclic synthesis

Fused O-heterocycles, synthesis via pericyclic reaction of o-quinodi-methanes 88YGK1179. 

Saturated O-heterocycles with P-containing substituents 82UK412. Silyloxydienes in total synthesis of natural O-heterocycles 81ACR400. Silylated N,O-heterocycles, synthesis of 80MI20. 

A final deviation reaction is given by the O-heterocyclic synthesis shown in Scheme 29. Here, it is thought that the ester group of one of... 

The first commercial synthetic dye, Mauveine (3), discovered by Perkin in 1856, was also a heterocycle, an azine of the Safranine class prepared by oxidation of aniline containing o- and p-toluidines. Since that time the contribution to colour chemistry from heterocyclic synthesis has been considerable and the present review can only hope to present some of the more salient features and at that only briefly. As an illustration it can be noted that since the late 1960s there have been in excess of 230 patents covering the use of azo dye couplers based on 2,6-dihydroxypyridine alone and the number of disclosures describing pyrazolones is probably greater than 1000. 

Preliminary results on the enantioselective formation of sulfur and nitrogen mediumsized heterocycles by base-induced ring opening of hetero-oxabicyclic [3.2.1] and [3.3.1] systems have been reported.91 The reaction involves a deprotonation-C—O bond elimination sequence. The kinetics and mechanism of gas-phase unimolecular elimination reactions of some substituted aminoazoles have been studied as an aid to heterocycle synthesis.92... 

Donald, D. S., Webster, O. W., Synthesis of Heterocycles from Hydrogen Cyanide Derivatives, 41, 1. 

Treatment of 5-bromo-3,4-dihydro-2ff-pyran with complex bases generates 3,4-dehydrodihydropyran (3), which reacts with ketone enolates to yield fused cyclobutanols (4) and the derived ketones (5) (95T1973). Both (4) and (5) are of value in the synthesis of polycyclic O-heterocycles (95SL742). 

Synthesis of N- and O-heterocycles, peri-fused naphthacenequinone derivatives 93UK1078. 

Synthesis of saturated N- and N,O-heterocycles by addition of nitrogen-containing reagents to alkenylsilanes 92MI38. 

Bicyclic ketals in stereocontrolled synthesis of 6 to 8-membered saturated O-heterocycles 92SL97. 

Ni(II)/Cr(II)-Mediated coupling reactions in synthesis of natural saturated O-heterocycles 92PAC343. 

Synthesis of quinone derivatives containing saturated O-heterocyclic substituents as 5-lipoxygenase inhibitors and antagonists of thromboxane A2 receptors 92YGK786. 

Synthesis of diterpenoids containing O-heterocyclic fragments 91MI41. 

Several approaches to what are formally Si-0 and O-Si-O heterocycles have been reported, although these reactions invariably involve the use of the Si-O bond only as a temporary tether. The coupling and RCM of dissymmetric alcohols was reported by Eustache and co-workers <01TL239> and this method was applied in the synthesis of attenol A <020L4105>. Denmark and Yang performed the RCM of Si-O tethered dienes in tandem with silicon-assisted cross-... 

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