New spiro phosphinooxazolines for palladium-catalyzed asymmetric allylic amination

Zn (II)/spiroQuinox catalyzed asymmetric Friedel–Crafts alkylation of indoles with cyclic N‐sulfonyl ketimino esters

“…We hypothesized that the N , N ‐ligands modified with a more rigid and bulky linker between the two coordinating sites could form more rigid metallocycle with fewer available conformations and thus enhance the enantiofacial differentiation. [ 10 ] Subsequently, the spiro ligands L3a – L3c and L4 – L6 were proposed and synthesized. The design strategies of the spiro ligands are outlined in Scheme 1.…”

Further Developments and Applications of Oxazoline-Containing Ligands in Asymmetric Catalysis

“…In 2018, Teng reported a new rigid phosphino­oxazoline ligand ( 248l,m ) possessing a chiral spiro core and it was applied in Pd-catalyzed asymmetric allylic alkylation and amination with ee s up to 99% (Scheme ). , …”

“…Tunge reported a method for the asymmetric allylic alkylation of α-tetralones via deacylative allylation using Pd(0) and (S)-tBu-PHOX (1) ligand (Scheme 23). 35 This method uses a readily available cyclic ketone pro-nucleophile (100) and allylic alcohol (101) as the allyl source. The reaction involves a retro-Claisen cleavage which results in the formation of both reactive intermediates, the active nucleophile (alkoxide) and electrophile (π-allyl).…”

Spiro Indane-Based Phosphine-Oxazolines as Highly Efficient P,N Ligands for Enantioselective Pd-Catalyzed Allylic Alkylation of Indoles and Allylic Etherification

“…Spiro phosphine-oxazoline ligands exhibit impressive catalytic performance in many cases by taking advantage of the chelating units of PHOX (phosphine-oxazoline ligands) and the spiro backbone. So far, there are four kinds of spiro phosphine-oxazoline ligands reported, including SIPHOX (spirobiindane-based phosphine-oxzoline ligands) by Zhou [25,26,27,28,29,30], SpinPHOX (spiro[4.4]-1,6-nonadiene-based phosphine-oxazoline ligands) by Ding [31,32,33,34], HMSI-PHOX (hexamethyl-1,1’-spirobiindane phosphine-oxazoline ligands) by Lin [35] and SMI-PHOX (an abbreviation for spiro mono-indane-based phosphine-oxazoline ligands L1 – L4 in Scheme 1) by us [36,37]. Compared with the other three ligands, SMI-PHOX ligands possess potentially distinct features: (i) first spiro indane-based phosphine-oxazoline ligand with non- C 2 -symmetric skeleton in asymmetric metal catalysis; (ii) better stability and higher rigidity; (iii) only one chiral center avoiding the complex stereochemistry; (iv) modularity by changing easily accessible carboxylic acid and ClPR 2 2 [36].…”

“…Compared with the other three ligands, SMI-PHOX ligands possess potentially distinct features: (i) first spiro indane-based phosphine-oxazoline ligand with non- C 2 -symmetric skeleton in asymmetric metal catalysis; (ii) better stability and higher rigidity; (iii) only one chiral center avoiding the complex stereochemistry; (iv) modularity by changing easily accessible carboxylic acid and ClPR 2 2 [36]. Because of the aforementioned properties, SMI-PHOX ligands have demonstrated excellent catalytic performance in several asymmetic reactions [36,37]. Therefore, we envisaged that they would be efficient chiral ligands for an indole C3-allylic alkylation reaction.…”