Gold‐Catalyzed Aldol and Related Reactions

Group 11 Metal Complexes with Unsymmetrical Bifunctional Ferrocene Ligands

“…The treatment of L2 with [Au(OTf)(PPh 3 )] gives the three‐coordinate mixed‐phosphine complex [Au{Fc(CH 2 PPh 2 )(PPh 2 )}(PPh 3 )]OTf ( 8 ) as an air‐ and moisture‐stable yellow solid. The synthesis of the three‐coordinate derivative 8 may be significant, as such a chelating coordination of these ligands to a gold center has always been proposed for the catalytic asymmetric aldol reaction and related reactions, and this complex could provide proof for this proposal . The IR spectrum shows the absorptions arising from the trifluoromethanesulfonate anion at ν̃ = 1272 [vs, br, ν as (SO 3 )], 1149 [vs, br, ν as (CF 3 )], and 1030 cm –1 [s, ν s (SO 3 )].…”

“…40 mL) and stirred for 30 min. Overnight refrigeration afforded L2 as a red airand moisture-stable solid, which was finally collected by filtration, yield 40 %, 1.71 g. C 35 …”

“…The synthesis of the three-coordinate derivative 8 may be significant, as such a chelating coordination of these ligands to a gold center has always been proposed for the catalytic asymmetric aldol reaction and related reactions, and this complex could provide proof for this proposal. [35] The IR spectrum shows the absorptions arising from the trifluoromethanesulfonate anion at ν = 1272 [vs, br, ν as (SO 3 )], 1149 [vs, br, ν as (CF 3 )], and 1030 cm -1 [s, ν s (SO 3 )]. The 1 H NMR spectrum shows the expected signals for the ferrocene and triphenylphosphine ligands in the appropriate ratio.…”

Gold(i)-catalyzed stereoselective cyclization of 1,3-enyne aldehydes by a 1,3-acyloxy migration/Nazarov cyclization/aldol addition cascade

“…4 In light of the mechanistic model, we wondered whether aldehydes incorporated into the starting enynes would be trapped in situ by C and form diquinanes ( 2 ) 5. The consequence of such a process is to add an unprecedented aldol addition reaction to the cascade that includes 1,3-migration and Nazarov cyclization 6. This would require that aldehydes in the starting enynes are compatible with and survive the intervening steps and thereby subsequently be engaged as electrophiles.…”

Total Synthesis of (−)‐Merochlorin A

“…Inspired by the work of Zhang on the synthesis of cyclopentenones from unfunctionalized, racemic enynyl acetates, we wondered whether 2 , including an aldehyde and a benzoyl‐protected primary alcohol, could be directly converted to 3 by a cascade of two successive ring closing reactions (Scheme b). This would involve 1,3‐acyloxy migration, Nazarov cyclization, and ultimately an unprecedented aldol reaction . We envisioned that the use of an optically active propargyl acetate could give enantioenriched 6 , provided that efficient transfer of chirality occurred during the initial two reaction steps.…”