Abstract
Reductive trimethylsilylation of pteridine and its deaza derivs. 1,4,6- and 1,4,5-triazanaphthalene and quinoxaline yields the primary reduced forms of these heterocycles, which contain the 1,4-dihydro-1,4-diazine ring with 8 conjugated p-electrons as the only low mol. wt. products. Although the organometallic substituents stabilize these biochem. important yet normally short-lived dihydro forms and so allow unambiguous characterization by NMR, the non-cryst., colored compds. are still highly reactive. Unexpectedly, the deaza derivs. prove to be less electron-rich than the silylated dihydropteridine despite a clear increase in the electron d. in the arom. ring. The characteristic conformational flexibility of these intermediates is responsible for this inverse annulation effect. Reductive trimethylsilylation of 1,5-naphthyridine yields the 1-trimethylsilyl-1,4-dihydro deriv. as the major product. on SciFinder(R)
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