engleski

Ninhydrin as a building block in scaffold-linked chromophoric dyad construction

The reaction of ninhydrin with ester-activated cyclobutene epoxide (CE-1) containing the fused 1, 4- dimethoxynaphthalene (DMN) chromophore, gave adducts formed by 1, 3-dipolar cycloaddition at the central (C2)-CO (major) and the outer (C1, 3)-CO (minor) positions. Conversion of the minor adduct to quinoxalines (QIN) by reaction with o-phenylenediamines at the a-dione moiety, albeit in poor yield, led to spiro-DMN-1, 4s-QIN dyad in which the plane of the chromophore was orthogonally orientated yet angled to the plane of the DMN chromophore. Reaction of ninhydrin with o-phenylenediamines yielded the corresponding 11-oxoindeno[1, 2-b]quinoxalines which were coupled with CE-BLOCKs to form spiro adducts by reaction at the carbonyl site ; the product from CE-1 was identical with that formed above. Another class of spiro-fused dyads was produced by reaction of ninhydrin with a primary amine followed by cycloaddition of CE-BLOCKs at the carbonyl site, where the amine was available to deliver one chromophore and the CE-BLOCK another.

ninhydrin; quinoxalines; cycloaddition reactions; chromophores; polycycles

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