Heterocyclic synthesis oxygen-containing

The key step in Biichi s total synthesis of loganin (5i)23 made use of the expansion of a four-membered ring to an oxygen-containing heterocycle by retro-aldol reaction. This strategy was later exploited by Tietze in his total synthesis of hydroxyloganin (54) as well as hydroxyloganic acid (55) 24). 

Synthesis of Oxygen-containing Derivatives of Sulfur Heterocycles by Catalytic Liquid-phase Oxidation V. P. Litvinov and T. V. Shchedrinskaya, Ratal. Sint. Org. Soedin. Sery, 1979, 27-37. 

Advances in the Synthesis of Oxygen-containing Heterocycles K. Fukui, Yuki Gosei Kagaku Kyokai Shi, 1966, 24, 741-754. 

There is a rich synthetic potential for enamines in heterocyclic synthesis. Enamines can react as electrophiles or nucleophiles and as new partners in cycloaddition reactions. Various derivatives of nitrogen-, oxygen-, and sulfur-containing heterocycles have been prepared, and these, in turn, are of interest as starting materials for additional syntheses. They represent potential synthons for the development of various new directions in organic chemistry. 

Unlike carbocyclic and oxygen-containing heterocyclic systems, catalytic enantioselective synthesis of eight-membered ring amines proceeds efficiently and with excellent enantioselectivity. These catalytic ARCM reactions can be carried out in the absence of solvent as well. Representative data regarding cat-... 

This section covers the synthesis of aziridines, oxiranes, /J-lactams and oxetanes. Aziridines are fairly important moieties in bioactive molecules and thus new routes for their synthesis are constantly being developed. /1-Lactams are probably the most important heterocyclic compounds that contain a single nitrogen atom, due to their importance in penicillin and cephalosporin chemistry. Their synthesis and chemistry has received much attention and much of this work has been reviewed544. The oxygen-containing heterocycles are much less commonly synthesized from double-bonded functional groups. 

The oldest known heterocycles are those containing oxygen as the hetero element. Kipping s work386) 382) with the first cyclosilanes (formed by a Wurtz synthesis from diphenyldichlorosilane) led to the discovery of two... 

The abundance of six-membered oxygen containing heterocycles in bioactive natural products continues to encourage the development of new and improved syntheses. There is a vast amount of new literature dedicated to the synthesis of pyrans and their benzo derivatives however, many traditional approaches are still of great value and this chapter should be read in conjunction with the corresponding chapters in the first and second editions of Comprehensive Heterocyclic Chemistry <1984CHEC, 1996CHEC-II>. 

In connection with the aforementioned reaction, Shea et al. reported the synthesis of [5,8,5]- and [5,7,5]-tricyclic oxygen-containing heterocycles via tandem Nicholas [35] and Pauson-Khand [23,24] reactions of acyclic enynes [36]. A typical Nicholas/[2 + 2 + 1] sequence is depicted in Scheme 12. 

Furfural (1), derived from annually renewable agricultural byproducts, is an important industrial chemical manufactured and used throughout the world. It is the feedstock for a number of derivative chemicals generically known as furans -the structural characteristic of which is the five-membered oxygen-containing heterocyclic ring. Furfuryl alcohol (2) is the most important derivative of commerce, where it is used primarily in synthesis of adhesive polymers. 

Oxazoles are well-investigated compounds. The occurrence, uses, and synthesis of oxazole derivatives have been the subjects of extensive reviews.5 The heterocyclic oxazole unit is seen with various substitution-patterns in a large number of naturally occurring compounds. Furthermore, oxazoles serve as synthetic intermediates leading to many other systems.5 6 7 In this context, oxazoles have seen, for example, numerous applications as "2-azadiene" components in 4+2 cycloadditions with several types of dienophiles. Further transformations of the products then lead to a number of other nitrogen- or oxygen-containing heterocyclic products.6... 

While the eight-membered ring proved to be an excellent precursor for the synthesis of oxygen-containing sulfur-nitrogen heterocycles with nu-cleophUes, as well as electrophiles, the five-membered rings have shown Lewis basicity on various substrates. 

The intramolecular O—H insertion reaction of a carbene has been successful in the synthesis of the oxygen-containing heterocycle 216 in quantitative yield (85JOC5223). Carbene generated by photolysis of diazo precursor 217 in protic solvents gives 2-phenyl-2,5-dihydroisobenzofuran competitively with insertion into the O —H bonds of the solvent (90JOC2325). 

A particularly useful general method for the synthesis of saturated nitrogen- and oxygen-containing partially unsaturated heterocycles, from 5-membered to medium ring-sized, is the Grubbs olefin metathesis applied, for example, to acyclic diaUcenyl-amines, as illustrated by syntheses of a dihydropyrrole and a tetrahydropyridine. ... 

The transition-metal-catalyzed reaction of diazo compounds 702, which have a N—H or O—H bond at an appropriate position, gives nitrogen- and oxygen-containing heterocycles 703 (Scheme 2 1 8).293 Wang and Zhu demonstrated a convenient synthesis of the polyfunctionalized /Tfluoropyrroles by the rhodium-catalyzed intramolecular N—H insertion reaction.2933 The reaction of d-amino-y,y-difluoro-a-diazo-/Tketo esters 704 in the presence of Rh2(OAc)4 gave the... 

V. The Synthesis of Oxygen-Containing Heterocycles by Intramolecular Cyclizations in... 

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