Syntheses of condensed pyrimidines as organic catalysts and the biomimetic redox catalyzed by them

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1) During the search for an efficient autorecycling oxidation catalyst, pyridodipyrimidine derivatives, new type NAD models, have been found to work under neutral conditions in oxidation of alcohols. This time, pyrimidopteridine derivatives as the catalysts, new type flavin models, were selected in the autorcycling oxidation. Actually, the pyrimidopteridines oxidized not only a variety of alcohols but also amines under neutral conditions at 120ﾟC for 10-25 hours to yield the corresponding carbonyl compounds and imines, catalytically with a markedly high turnover number (ca.20-180 turnover number).2) The biomimetic reduction of carbonyl compounds by NADH models such as N-alkylnicotinamides or Hantzsch esters has been extensively studied. However, these NADH models can reduce only carbonyl compounds which are highly activated by the presence of electron-deficient or by the presence of metal ions. In 1978, Yoneda et al.were reported first example of the reduction of inactivated simple carbonyl substrates to the corresponding alcohols by 1,5-dihydro-5-deazaflavin in the presence of strong proton sources such as hydrochloric acid or trifluoroacetic acid in stoichiometric yields. We studied now the autorecycling reduction of carbonyl compounds to alcohols by 1,5-dihydro-5-deazaflavins which are produced by 5-deazaflavin and formic acid in a circulatory system. In particular, the reduction using 3,7-dimethyl-10-p-tolyl-5-deazaflavin at 120ﾟC for 50 hours proceeded until the benzaldehyde substrate was exhausted to give 100% yield of benzyl alcohol. The yield based on the catalyst was 3129%, which means 31 recyclings of the catalyst. Morcover, a useful autorecycling system for the specific 1,4-reduction of alpha, beta-unsaturated carbonyl compounds to the corresponding saturated carbonyl compounds catalyzed by the 3,7-dimethyl-10-p-tolyl-5-deazaflavin in formic acid was studied.