Catalytic enantioselective [2+2]-cycloaddition reaction of 2-methoxycarbonyl-2-cyclopenten-1-one by chiral copper catalyst

Cyclobutane and Cyclobutene Synthesis: Catalytic Enantioselective [2+2] Cycloadditions

“…[29] In efforts towards the total synthesis of (+ +)-tricycloclavulone (72), Iguchi and co-workers developed ac atalytic enantioselective [2+ +2] cycloaddition of the alkynyl sulfide 70 and cyclopentenone derivative 69 (Scheme 10). [30] Thec hiral ligand 73 in combination of CuCl 2 and AgSbF 6 was identified to be optimal after more common chiral catalysts (e.g., Ti/ TADDOL and Cu/BOX)w ere found to be ineffective.T he substrate scope of this process has not yet been reported. However,subsequent studies utilized this method toward the formal synthesis of (+ +)-precapnelladiene.…”

“…[54,55] In addition, the utility of these methods has only rarely been demonstrated in the synthesis of complex molecules. [22,30] Continued efforts in these areas will undoubtedly lead to fundamentally new methods and an increase in the scope and practicality of existing strategies.…”

Electrophilic Functionalization of Non-Activated Olefins Catalyzed by Lewis Superacids

“…55 The related reaction of activated olefins such as 10 with arylthioacetylenes such as 11 was successfully carried out by using copper(II) triflate (Scheme 7). 56 The addition of chiral bis-pyridine ligands allowed the formation of enantiomerically enriched products, though with low optical yields, the best results being obtained with a combined CuCl 2 -AgSbF 6 -chiral ligand system. This methodology was further successfully applied to the enantioselective total synthesis of (+)-tricycloclavulone.…”

Addition Reactions: Cycloaddition

“…This catalytic system was applied to the enantioselective total synthesis ee of the marine prostanoid tricycloclavulone. 27 An ab initio study of the 2 + 2-cycloadditions of allene to isocyanic acid and ketene to vinylimine found the reactions to be concerted and mostly asynchronous. 28,29 The diastereoselective 2 + 2-cycloaddition of dichloroketene with a chiral enol ether (26) produced the cyclobutanone (27), which leads to a key intermediate (28) in de the total synthesis of the natural alkaloid (−)-Swainsonine (29) (Scheme 8).…”

“…27 An ab initio study of the 2 + 2-cycloadditions of allene to isocyanic acid and ketene to vinylimine found the reactions to be concerted and mostly asynchronous. 28,29 The diastereoselective 2 + 2-cycloaddition of dichloroketene with a chiral enol ether (26) produced the cyclobutanone (27), which leads to a key intermediate (28) in de the total synthesis of the natural alkaloid (−)-Swainsonine (29) (Scheme 8). 30 (32), which readily underwent Cope rearrangement to substituted 5,6-dihydro-1H -azocinones (33) in high yields (Scheme 9).…”