Diaza derivatives

Halogen-metal exchange has also been performed in the absence of an N-substituent, as was shown by the lithiation and derivatization of the diaza derivative 5-bromo-4-chloro-7//-pyrrolo[2,3-c(]pyrimidine (Scheme 26K90JMC1984). 

In another synthesis, the Vilsmeier salt (63) with aqueous methyl-amine gave the aza compound (64). The methyl iodide adduct of 64 was afterward reacted with methylamine, forming the diaza derivative (65).83... 

Carbodiimides are diaza derivatives of C02. It is also possible to add heteroatom nucleophiles to them. This is especially relevant when the heteroatom nucleophile is a carboxylic acid and when the carbodiimide is dicyclohexylcarbodiimide ... 

In addition, Ihe papers by Longuet-Higgins and Coulson give ir densities for every position in every diaza derivative of anthracene and phenanthrene (47TFS87 49JCS97I). 

Lastly, the mixed tetraoxo-diaza derivative of 18-crown-6, diaza-18-crown-6, has also been utilized to stabilize aluminum atoms in high coordination environments. In particular, the [(EtAl)2 diaza-18-crown-6] " " cation displays the aluminum center in a rare square pyramidal... 

A 93% yield of a unique bis-silylene complex is obtained when a cyclic diaza derivative is combined with a metal carbonyl (b). 

As to the electronic effect of the nitrogen atoms adjacent to the benzylic center in the diaza derivative 7d, semiempirical calculations show that only 2% of the a. spin density is delocalized onto the nitrogens of the urazole moiety. Therefore, the urazole-bridged derivatives 7 are localized triplet diradicals and their lower D values (Table 5) derive from the slightly lower spin densities and the somewhat higher interradical distance dAB. The latter is a consequence of angle widening due to the shorter N—N versus C—C distance ( 144 vs. 154 pm [67]). 

This symmetrical molecule is the 5,8-diaza derivative of quinoxaline. An alternative name frequently used for this heterocycle is 1,4,5,8-tetraazanaphthalene. Completely reduced derivatives of the ring system have been called piperazinopiperazines and naphthopiperazines. 

Further reaction of the 4-aza-isomer (400) with the same reagents gave the 4,6-diaza-derivative (402). " Hydrazoic acid with Bp3-ether converted 25R)-spirost-4-en-3-one into the tetrazole derivative (403). The tetrazole was sufficiently stable to survive conventional degradation of the spirostan system to give pregnane and androstane analogues. ... 

CE separations and forms complexes with chiral analytes in a way similar to CDs, based on differences in complex formation energies. Two new 18-crown-6 diaza derivatives were investigated as chiral selectors [120]. These derivatives did not show any chiral selectivity toward the investigated analytes, they could serve well as an additive to improve the chiral resolution in combination with CDs. 

The isomerization of vibrationally excited photofragments was first studied in detail by Steel, Schlag, and others in their studies of the photodissociation of ring systems such as the diaza-derivative (1) and cyclo-butanone. 

Table 7.51. i c Coupling constants of diaza derivatives - Obtained in N-NMR... 

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