Origin of Stereocontrol in the Construction of the 12-Oxatricyclo[6.3.1.02,7]dodecane Ring System by Prins−Pinacol Reactions

• Published in: Journal of organic chemistry Vol. 75; no. 2; pp. 455 - 463
• Main Authors: Overman, Larry E, Tanis, Paul S
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 15.01.2010; Amer Chemical Soc
• Subjects: Alkanes - chemistry; Chemistry; Chemistry, Organic; Cyclization; Heterocyclic Compounds, 3-Ring - chemistry; Molecular Structure; Physical Sciences; Polycyclic Compounds - chemistry; Science & Technology; Stereoisomerism; NUCLEOPHILIC-SUBSTITUTION REACTIONS; STRATEGIC USE; ACETALS; CYCLIZATIONS; DOMINO
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo9024144

Polycyclic products containing the 12-oxatricyclo[6.3.1.02,7]dodecane moiety having either the trans (8a−e) or cis (9a−e) relative configuration of the oxacyclic bridge and the cis angular substituents are formed stereospecifically by Prins−pinacol cyclizations of unsaturated α-dithianyl acetals 14a−e or 15a−e. These results show that the topography (boat or chair) of the Prins cyclization of the sulfur-stabilized oxocarbenium ions generated from acetals 14a−e or 15a−e is controlled by the stereoelectronic influence of the allylic substituents, with steric effects playing a minor role. A complex molecular rearrangement that is terminated by a thio-Prins−pinacol reaction is also identified.