Diastereoselective Intermolecular Pauson−Khand Reactions of Chiral Cyclopropenes

Abstract

In this Letter, it is demonstrated that the unusual reactivity of cyclopropenes can increase the scope and utility of intermolecular Pauson-Khand reactions. The well-defined chiral environment of cyclopropenes has a powerful influence on the diastereoselectivity of the reactions and leads to the production of a single cyclopentenone in each of the described cases. The cyclopropane ring strongly influences the stereochemistry of reactions at the enone, and the three-membered ring can subsequently be cleaved under mild conditions. [reaction: see text]

Transition metals in organic synthesis: Highlights for the year 2005

“…Diastereoselective intermolecular Pauson-Khand reactions of chiral cyclopropenes were described [996]. Asymmetric cobalt-catalyzed intermolecular Pauson-Khand reactions were reported [997].…”

One‐pot Synthesis of Aromatic Fused 2,3‐Dihydroindanone by Tandem Pauson‐Khand/Michael/Henry Reaction

“…[16][17][18] Mild alkyl methyl sulfide (n-BuSMe, PhSMe, n-C 10 H 21 SMe) also only gave low to moderate yields of 24%-58% (Entries 3-5), which might be attributed to the bulky phenyl substitute in the cobalt-alkynl complexes hindering the approach of bulk promoters. [19,20] Thus, a "smaller" promoter DMS (dimethyl sulfide) was used and worked with improved yields (Entries 6, 7), and xylene was also a nice solvent (Entry 8). Since α,β-unsaturated aldehydes/ketones readily undergo 1,2-addition with nitroalkanes under basic conditions, both the activation of carbonyl group and the controlling of proper pH are crucial to gain the Michael addition reaction product.…”

Cyclopropanation

“…Yet another powerful method for achieving high regio-and stereoselective cyclopropanation is the Pauson-Khand reaction. In the presence of chiral cyclopropenes, and BuSEt as a promoter, an enantiomerically pure cyclopentenone was obtained in good yield and with excellent enantioselectivity (Scheme 38) (134). In addition, the cyclopropyl ring cleavage was also demonstrated under mild condition.…”