Five with three heteroatoms

VI. Five Membered Heterocyclo-Quinolines with Three Heteroatoms. 162... 

Five-Membered Heterocycles with Three Heteroatoms 6.24.5.1 1,2,3-Triazoles... 

Five-Membered Heterocycles with Three Heteroatoms 246... 

Fig. 3.8 Five-membered heteroq cles with three heteroatoms obtained by solid-phase chemistry...

Applications of five-membered tin heterocycles with three heteroatoms are widespread and the subject of numerous papers and patents. However, practically all publications are devoted to only one type of compound, the readily available 1,3,2-diheterastannolanes. 

Five-Membered Rings with Three Heteroatoms. 

Five-Membered Rings with Three Heteroatoms. 344... 

V. Quinones with a Condensed Five-Membered Ring with Three Heteroatoms... 

DIMEDONE-ANNULATED FIVE-MEMBERED HETEROCYCLES WITH THREE HETEROATOMS... 

Because these transition state structures are symmetric, all previously used approaches for determining relative reactivity of the heterocycles should be applicable in these cases. The cycloaddition is a HOMO dienophile and LUMO heterocycle (diene) controlled cycloaddition reaction with exceptionally low demand for orbital energy changes in reactants to achieve the electronic contribution present in the transition state structure (Table 41). There is no doubt that 1,3,4-oxadiazole is the most reactive of all five-membered heterocycles with three heteroatoms. However, the question remains as to whether this heterocycle is more reactive than, for instance, furan or even cyclopentadiene. To answer this question, the deviation of bond order uniformity in the six-membered ring being formed was computed (Table 42). The bond order uniformity selected 1,3,4-... 

Application of Ionic Liquids in Heterocyclic Synthesis 4 1 Synthesis of Five-Membered Heterocycles 4.1.1 Synthesis of Five-Membered Heterocycles 443 443 with Two Heteroatoms 4.2.3 Synthesis of Six-Membered Heterocycles with Three Heteroatoms 4.3 Synthesis of Some Other Spiro Heterocycles 468 479 480... 

SCHEME 25 Synthesis of benzimidazole-based poly(ADP-ribose) polymerase-1 inhibitors. TABLE 2 Microwave-Induced Synthesis of Five-Membered Heterocyclic Ring with three Heteroatoms... 

Besides the above, a few more fherapeutically advantaged heterocyclic systems, synthesized by green heating (microwave irradiation) protocol, were found in the literature. In all tiie cases, dielectric heating was applied to S5mthesize the five-membered heterocyclic ring with three heteroatoms. These are summarized in Table 2 (Fig. 13). 

Numerous examples of the ring closure of a binucleophilic system with a 1,1 -bielectrophile leading to five-membered heterocycles with three or more heteroatoms have been described, the popularity of this route no doubt reflecting the comparative ease with which the penultimate product may be obtained. 

Three systems were pyrazoles are condensed to five-membered rings with one heteroatom exist (300-302). For pyrrolopyrazoles, a fourth iso-merer (303) is also possible. When the pyrazole ring is fused to a heterocyclic system in which the heteroatom is tetravalent, several isomeric structures can be drawn. Derivatives of 300-303 can be prepared either... 

A series of five-membered heterocycles with two and three heteroatoms were synthesized. 4-Hydroxyisothiazoles 57 were prepared from a-amino ketones with sulfur monochloride (1968BCJ959). Polar solvents, especially N,Af-dimethylfor-mamide, were preferable (Scheme 28). In a similar reaction of 1-amino-l-phenyl-2-propanone with sulfur monochloride 5-chlorinated isothiazole 58 was obtained in high yield. 

In addition, five heterodiphospholes (T-X) are known and are also dealt with in this chapter. Within the scope of this chapter are five-membered rings with three and four phosphorus atoms but no other heteroatoms. In these systems, full cyclic conjugation can only be attained if all phosphorus atoms are two-coordinate. The ring consequently must be negatively charged as in the 1,2,4- and 1,2,3-triphospholides (Y, Z) and in the tetraphospholides (iE). The pentaphospholide (0) is again beyond the definition but must not be excluded here. 

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

Unsaturated and saturated compounds are considered in the same sections since the number of five-membered heterocycles with three and more heteroatoms (and especially their structure types) is limited and their reactivity does not differ fundamentally. 

In Section 4.24.2 the literature from 1982 to the beginning of 1994 (according to Chemical Abstracts) is considered. Earlier data concerning five-membered rings with three or more heteroatoms including at least one Ge, Sn or Pb atom are scarce and there is no information in CHEC-I on these heterocycles. Valuable data on germanium heterocycles can be found in the monograph by Lesbre et al. 424-01 > and some of these data have been included in this section. Tin and... 

Main data on various routes for the synthesis of particular classes of five-membered germanium, tin and lead heterocycles with three and more heteroatoms were given and compared in Sections 4.24.2.6 and 4.24.2.7. In Tables 3-8 the synthetic routes are classified according to the nature and number of heteroatoms. Some references are included for completeness from the monograph [Pg.891]

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