The dihydropyran 3 reacts with sulfonyl azides to give the known (sulfonylimino)‐ethers ( = lactone sul‐fonylimines) 4 and 18. Reaction of 4 with NH2NH2 · H2O leads to the aminoiriazole‐dibulanol 5, characterized as its tetraacetate 8, and not, as previously claimed, to 6 or 7. Similarly, the dihydrofuran‐derived (tosylimino)‐ether 10 yields 11 The structure of 5 was established by X‐ray analysis, and a mechanism for its formation is proposed. Reaction of 4 with NH2NMe2 afforded the lactone hydrazone 16 and the hydrazidine 17. Catalysis by imidazole suppressed the formation of 17similarly, the [(trifluoromethyl)sulfonyl]imine 18 yielded 16, and, by reaction with NH2N(Me)Ph or 4‐amino‐4H‐1,2,4‐triazole, the lactone hydrazone 19 and the adduct 20, respectively. The 1,4‐lactone hydrazone 21 was obtained from 10 or from 22. The structure of 20 was established by X‐ray analysis. Treatment of 16 with BuLi followed by BnBr yielded the α‐alkylated lactone hydrazone 23.

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The synthesis of a-benzamido-a-benzyl lactones 23 of various ring size was achieved either via 'direct amide cyclization' by treatment of 2-benzamido-2-benzyl-x-hydroxy-N,N-dimethylalkanamides 21 in toluene at 90 -110°with HCl gas or by 'ring transformation' of 4-benzyl-4-(x-hydroxyalkyl)-2-phenyl-1,3-oxazol-5(4H)-ones under the same conditions. The precursors were obtained by C-alkylations of 4-benzyl-2-phenyl-1,3-oxazol-5(4H)-one (15) with THP-or TBDMS-protected xhydroxyalkyl iodides. Ring opening of the THP-protected oxazolones by treatment with Me 2 NH followed by deprotection of the OH group gave the diamides 21, whereas deprotection of the TBDMS series of oxazolones 25 with TBAF followed by treatment with HCl gas led to the corresponding lactones 23 in a one-pot reaction.

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