Recent advances of achiral and chiral diene ligands in transition-metal catalyses

Synthesis of Rhodium Complexes with Chiral Diene Ligands via Diastereoselective Coordination and Their Application in the Asymmetric Insertion of Diazo Compounds into E−H Bonds

“…The results clearly showed that the new ligands i Pr 2 ‐TFB ( 1 c ) and t Bu 2 ‐TFB ( 1 d ) are more bulky (judging by the total buried volume V buried ) and more asymmetric (judging by the difference between V buried of the most and the least occupied quadrants) than the previously used ligands Me 2 ‐TFB [26] and Ph 2 ‐TFB [20] . To the best of our knowledge, the t Bu 2 ‐TFB ligand has the largest total buried volume ( V buried =58 %) of all known chiral dienes (compare for example to V buried =48 % for simple 1,5‐cyclooctadiene and V buried =52 % for bulky 2,5‐diphenyl‐norbornadiene) [2] …”

“…The second enantiomer S , S ‐ 2 c was initially obtained in 37 % yield and with 84 % ee , which was then enhanced to >99 % ee by single recrystallization. It is important to emphasize that unlike most known methods [1, 2] our approach provides easy access to both enantiomers of the chiral diene complexes. The same procedure allowed us to obtain the more bulky chiral complexes [( R , R ‐ t Bu 2 ‐TFB)RhCl] 2 ( R , R ‐ 2 d ) and [( S , S ‐ t Bu 2 ‐TFB)RhCl] 2 ( S , S ‐ 2 d ) with >99 % ee .…”

“…[20] To the best of our knowledge,t he tBu 2 -TFB ligand has the largest total buried volume (V buried = 58 %) of all known chiral dienes (compare for example to V buried = 48 %for simple 1,5-cyclooctadiene and V buried = 52 % for bulky 2,5-diphenyl-norbornadiene). [2] In order to separate the racemic diene complexes,i tw as necessary to find ac hiral auxiliary ligand L, which would coordinate selectively with one of the enantiomers of [(R 2 -TFB)RhCl] 2 .T od ot hat we calculated the difference in the thermodynamic stability of the corresponding diastereomeric adducts (R,R-tBu 2 -TFB)Rh(L) and (S,S-tBu 2 -TFB)Rh(L) by DFT methods for various ligands Li ncluding L = S-proline (0.03 kcal mol À1 ), N-isopropyl-S-proline (2.77 kcal mol À1 ), diphenyl-S-prolinol (1.05 kcal mol À1 ), diphenylphosphanyl-R-BINOL (0.29 kcal mol À1 )a nd some other (Supporting Information). As the result of this screening,w ec hose isopropylsalicyloxazoline (S-Salox) as one of the most convenient and effective auxiliary ligands (Table 1).…”

“…Thed evelopment of enantioselective catalysis largely relies on ad iversity of the available chiral ligands.C hiral dienes (Scheme 1) have distinct electronic and steric properties which make them effective ligands for many reactions. [1,2] In particular,r hodium complexes with chiral dienes are among the best catalysts for asymmetric addition of arylboronic acids to the enones,i mines,a nd other polar double bonds. [3][4][5] Although these catalysts have shown aremarkable performance,t heir accessibility is still rather limited.…”

4-exo-dig cyclocarbopalladation, discovery and application in the synthesis of complex polycyclic molecules

“…This motif is hardly represented in Nature, and Caulerpin, a bis-indole alkaloid isolated from algae of the genus Caulerpa, is the only representative. 21 Nevertheless, COTs display important properties, especially as ligands in the field of metal-catalyzed processes 22 or in the field of materials. 23 The development of metal mediated syntheses to access highly substituted COTs has been investigated and when we started our investigation in the field, the challenge was the synthesis of fully substituted, unsymmetrical COTs with structural complexity.…”