A new synthesis of flavins

Copper-Mediated 3-N-Arylation of Flavins

“…To extend the 3-N-arylation reaction to other flavins, tetraacetylriboflavin 1b 25 was used as the starting material (entry [16][17]. At room temperature, 39% of N-phenylflavin 3b-H was obtained after two days; 16% after two hours in a microwave reaction.…”

“…11d, [15][16] So far, only few examples are known with aryl substitution at the 3-N position. [17][18][19][20][21][22] However, introduction of these aryl substituents requires additional steps before the flavin ring system is cyclized. Direct arylation of flavins at this position may provide a short cut creating valuable flavin derivatives.…”

Synthesis of a new hetrocyclic system 7,8-dihydroimidazo[1,2-c][1,3]oxazolo[4,5-e]pyrimidine

“…The central tricyclic system O (1)N(1-4)C(1-7) is approximately planar, the deviation of atoms from the mean square plane did not exceed 0.047 Å. Furthermore, even the exocyclic benzene ring C (8)(9)(10)(11)(12)(13), in spite of the obvious steric hindrance, was practically coplanar with this system (the appropriate dihedral angle was only 3.2 o ), which is caused by efficient π-π conjugation. The N(3) and N(4) atoms have a plane-trigonal bond configuration, the corresponding sum of valence angles at these atoms amounts to 359.…”

“…As a result of the favorable disposition of the nitrile group and the acylamino residue in compounds 3 the possibility arises of an intramolecular cyclization under the action of trifluoroacetic acid (see [7][8][9]) into new derivatives of oxazole 4, which exist preferentially in the tautomeric form 5. Attempts to introduce compound 3e into this cyclization with an acetylamine residue were unsuccessful, a mixture of unidentified substances was formed.…”