Seven-membered and larger heterocycles

The transition metal catalyzed synthesis of seven membered and larger heterocycles attracted considerably less attention than the preparation of their five and six membered analogues. Typical examples in this chapter include the formation of heterocycles in insertion reactions, or through carbon-heteroatom bond formation. Although the formation of some macrocyclic natural products was also achieved in cross-coupling reactions they will not be discussed in detail. 

The heterepine-heteronorcaradiene equilibrium exemplifed for oxepin in Scheme 2 represents perhaps the best known type of valence tautomerism met in seven-membered and larger heterocyclics. 

Volume 9 covers seven-membered and larger heterocyclic rings including all fused derivatives (except those with three- or four-membered rings which are included in Volume 1). 

Relatively few examples of photoreactions of seven-membered and larger heterocycles have been reported. The major products of irradiation of liquid oxepin are hex-5-en-l-ol and hexanal234 photodecomposition of cyclic ethers has, in general been shown to be largely dependent on ring size. Irradiation of the valence bond isomer (287) of hexakis(trifluoromethyl) oxepin gave the unexpectedly stable oxet (288) via a mixture of (Z)- and... 

D. Radicals Containing Seven-Membered AND Larger Heterocycles... 

Table 1 Seven-membered and larger arsenic heterocycles...

The chemistry of the E-Hlg (E=As, Sb, Bi) bonds has been featured prominently in the reported chemistry of seven-membered and larger rings containing arsenic, antimony, and bismuth. In work directed toward the synthesis of heterocyclic systems involving transannular Sb N interaction, 64 and 65 have been obtained from chloro-substituted stibocanes 63a by reaction with LiPh in hexane or NaOSiPh3 in toluene. To obtain the NCS-substituted 66, the iodo-substituted stibocanes 63b were reacted with AgSCN in dichloromethane (Equation 2) <1998POL2655>. 

SEVEN-MEMBERED AND LARGER RING-FLUORINATED HETEROCYCLES... 

Since perfluorinated heterocycles have distinct and often unique chemistry, this group was considered as a separate category and data on perfluorinated aromatic and nonaromatic compounds are given in Chapters 8 and 9, respectively. The information on seven-membered and larger ring heterocycles, including perfluorinated crown ethers and polyfluorinated macrocycles, is provided in Chapter 10, which concludes Part I of the book. 

SEVEN-, EIGHT-MEMBERED AND LARGER HETEROCYCLIC RINGS AND THEIR FUSED DERIVATIVES... 

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