In the introduction, a brief survey is given of the main types of fused‐skeleton saturated six‐membered 1,3‐heterocycles serving as model compounds in our earlier investigations and as starting compounds in the present studies. The synthesis and conformational analysis of aryl‐substituted fused‐skeleton saturated 1,3‐oxazines and of aryl‐substituted hetero‐condensed saturated isoindolones are treated. cis‐trans isomerization in the saturated isoindolone moiety of the resulting tricyclic, tetracyclic and pentacyclic systems is discussed in connection with the ring‐closure reactions of cis‐ and trans‐1,2‐disubstituted 1,2‐ and 1,3‐difunctional alicyclic compounds to give alicycle‐fused six‐membered 1,3‐heterocycles. The cycloaddition reactions of dihydro‐1,3 and 3,1‐oxazines and the conformations of the alicycle‐fused tetrahydrooxazine‐azetidinone derivatives obtained are presented. Methods are given for the preparation of saturated thiazolo‐ and thiazino[2,3‐b]quinazolinones. Unambiguous, mainly one‐pot syntheses for the preparation of 1,3‐heterocycles by a retro Diels‐Alder method are discussed.
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