(3+3)‐Annulation of Carbonyl Ylides with Donor–Acceptor Cyclopropanes: Synergistic Dirhodium(II) and Lewis Acid Catalysis

Abstract

The first (3+ +3)-annulation process of donoracceptor cyclopropanes using synergistic catalysis is reported. The Rh 2 (OAc) 4 -catalyzed decomposition of diazoc arbonyl compounds generated carbonyl ylides in situ. These 1,3dipoles were converted with donor-acceptor cyclopropanes, activated by Lewis acid catalysis,toaffordmultiply substituted pyran scaffolds in high yield and diastereoselectivity.Extensive optimization studies enabled access to 9-oxabicyclo-[3.3.1]nonan-2-one and 10-oxabicyclo[4.3.1]decen-2-ol cores, exploiting solvent effects on intermediate reactivity.

(3+3)‐Annulation of Carbonyl Ylides with Donor–Acceptor Cyclopropanes: Synergistic Dirhodium(II) and Lewis Acid Catalysis

“…Ther esulting annulation products 3da and 3db showed 93 %a nd 94 % ee, respectively.T he absolute configuration of 3db (5R,8 R,9 R)w as elucidated by X-ray diffraction analysis and was found to be the respective inversion product. [17] These results suggest as tereospecific annulation process (Scheme 3; for further mechanistic investigations see the Supporting Information).…”

Ferrocenyl-substituted tetrahydrothiophenes via formal [3 + 2]-cycloaddition reactions of ferrocenyl thioketones with donor–acceptor cyclopropanes

“…However, in contrast to 8a, the reaction of 8b with 5a was unsuccessful. This observation prompted us to replace AlCl 3 by scandium triflate (Sc(OTf) 3 ), which is also known to be an efficient catalyst in various reactions of D-A cyclopropanes [9,10,20]. This time, the reaction was complete after 1 h and the expected 2,2-diferrocenyl-substituted tetrahydrothiophene 9b was isolated chromatographically in about 28% yield (Scheme 3, Table 1).…”

Ferrocenyl-Substituted Tetrahydrothiophenes via Formal (3+2)-Cycloaddition Reactions of Ferrocenyl Thioketones With Donor-Acceptor Cyclopropanes

“…As the next model substrate, the sterically crowded diferrocenyl thioketone (8b) was tested as a structural analogue of thiobenzophenone, which is widely applied in studies involving aromatic thioketones [3][4][5]. However, in contrast to 8a, the reaction of 8b with 5a was unsuccessful; this observation prompted us to replace AlCl3 by scandium triflate (Sc(OTf)3), which is also known to be an efficient catalyst in various reactions of D-A cyclopropanes [9,10,19]. This time, the reaction was complete after 1 h and the expected 2,2-diferrocenyl-substituted tetrahydrothiophene 9b was isolated chromatographically in about 28% yield (Scheme 3, Table 1).…”