An Expedient Route to New Spiroheterocycles: Synthesis and Structural Studies

Abstract We have developed a short, efficient and enantioselective synthesis of 1,4,7,10‐tetraoxa‐ and 1,7‐dioxa‐4,10‐dithiaspiro[5.5]undecanes. The method involved the reaction of solketal 5 or thiol derivative 6 with 1,3‐dichloropropanone O ‐benzyloxime ( 4 ) which affords the conveniently protected symmetrical ketones 7 and 8 . Elaboration of the required 4,10‐disubstituted‐1,7‐dioxaspiro[5.5]undecane systems 1 and 2 entailed a final “one‐pot” deprotection–spirocyclization process in an acidic medium. The structures and configurations of the spiroketals were established unambiguously by NMR spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)