Five with four heteroatoms

Vll. Five Membered Heterocyclo-Quinolines with Four Heteroatoms. 173... 

Five-Membered Heterocycles with Four Heteroatoms... 

Five-membered heterocycles with four heteroatoms are also known. Apart from tetrazole, there are four structurally isomeric oxatriazoles and thiatriazoles ... 

Synthesis of Five-Membered Heterocycles with Four Heteroatoms 4.1.4.1 Tetrazoles... 

Table 1 X-Ray Structures of Compounds with Five-membered Rings and Two, Three or Four Heteroatoms ...

FIVE-MEMBERED RINGS WITH THREE OR FOUR HETEROATOMS INCLUDING AT LEAST ONE GROUP IV HETEROELEMENT OTHER THAN SILICON... 

FIVE-MEMBERED RINGS WITH THREE OR FOUR HETEROATOMS... 

The discovery of metallic conductivity in organic solids stands as a major scientific discovery of the twentieth century <1995S215>. From a total of several organic 7t-donors described in the literature, five (438a-c, 439, and 440) are four-heteroatom bicyclic 5 6 systems with two heteroatoms in each moiety. 

Other Four Heteroatoms 2 2 Five or More Heteroatoms Tricyclic Systems Central Carbocyclic Ring with Fused Five-membered Rings Tricyclic Systems Central Carbocyclic Ring with Fused Five- and Six-membered Rings Tricyclic Systems Central Carbocyclic Ring with Fused Six-membered Rings... 

Seven-membered rings with four and more heteroatoms attract attention because of their biological activity. An important class of compounds is that of the seven-membered cyclic polysulfides with five sulfur atoms, which are well known as lenthionine and varacin. 

The compounds with five-membered rings containing three or four heteroatoms including at least one phosphorus were first systematically reviewed in Chapter 4.22 of CHEC-II(1996) by Schmidpeter <1996CHEC-II(4)771>. In CHEC(1984), only few examples of 2//4,2,3-diazaphospholcs were mentioned in the general chapter on phosphorus heterocycles <1984CHEC(1)493>. 

Figure 1 Silicon-containing five-membered heterocycles with three or four heteroatoms.

Table 1 X-Ray crystal structures of five-membered rings with three or four heteroatoms including at least one group III or IV metal deposited to CCDC between 1995 and 2005... 

The major synthetic routes for the preparation of five-membered group III and IV metal-containing heterocycles with three or four heteroatoms are illustrated in the text and in Table 1. 

The chemistry of cyclopentafurazans (cyclopen-ta-1,2,5-oxadiazoles) and furazans fused to five-membered heterocycles with one to four heteroatoms has been reviewed (95JHC371). Treatment of 3-amino-4-nitro-l,2,5-oxadiazole with dinitrogen pentoxide yields dinitro-1,2,5-oxadiazole 89 (95MC102). The latter reacts normally with benzenethiol to give the sulfide 90,... 

Section 3.1 is a brief overview Section 3.2 deals with six-membered heterocycles, including those with more than one heteroatom in the ring Section 3.3 deals with five-membered heterocycles with one heteroatom Section 3.4 deals with five-membered heterocycles with more than one heteroatom in the ring Section 3.5 covers small (three- and four-membered) and large (>six) ring heterocycles. 

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