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A method was proposed for estimating the possibility of cyclization of adducts of resorcinol with pyrimidines to form oxadiazocines based on the conformational criterion and analysis of charges on the C1'5~ atom of the pyrimidine ring and on the H atom of the hydroxy group of the resuhing adducts. A series of new deri,,atives of 4.5-dihydro-I I H-5,1 Imethanobenzolglazololl,3,5}oxadiazocines were synthesized. Aromatic electron-excess compounds (indoles, furans, pyrroles, thiophenes, phenols and their ethers, etc.) add to pyrimidine systems tinder conditions of acid catalysis) In most cases, these reactions afford rather stable ~-adducts and can be used for direct functionalization of various pyrimidine derivatives with fragments of aromatic and heteroaromatic compounds. When binucleophilic agents are used. the adducts that formed initially can undergo further conversions. ThtLs the reactions of pyrimidine derivatives (la,b) and quinazoline (It,d) with resorcinol (2) are stopped in the stage of formation of adducts (3a--d) (Scheme 1), while the reactions of other pyrimidines (le--i) give oxadiazocines (4e--i). The possibility of the synthesis of these cage structures attracts attention from the viewpoint of the novelty of the resulting heterocyclic systems as well as of their potential biological activity. The synthetic potential of this reaction is still not completely realized, because reactions of resorcinol with annelated heterocycles containing the pyrimidine ring have not been studied yet.The aim of the present work was, first, to search for calculation criteria which would allow the prediction of the possibility of resorcinol adducts with pyrimidine systems undergoing cyclizati0n and, second, to search for reaction conditions and to prepare new Siructures by the reactions of azoloannelated pyrimidines with resorcinol.In the theoretical studies of the possibility of cyclization of resorcino[ adducts with pyrimidine systems, we considered the smmtures of adducts 3a--i, for which 9 t?experimental data are available in the hterature, ,-and the structures of adducts 6a--f. the possibility of cyclization of which was examined in the present work.