PdII-Catalyzed Site-selective β- and γ-C(sp3)-H Arylation of Primary Aldehydes Controlled by Transient Directing Groups
Pd(II)-catalyzed site-selective β- and γ-C(sp3)-H arylation of primary aldehydes is developed by rational design of L,X-type transient directing groups (TDG). External 2-pyridone ligands are identified to be crucial for the observed reactivity. By minimizing the loading of acid additives, the ligand effect is enhanced to achieve high reactivities of the challenging primary aldehyde substrates. Site selectivity can be switched from the proximate to the relatively remote position by changing the bite angle of TDG to match the desired palladacycle size. Experimental and computational investigations support this rationale for designing TDG to potentially achieve remote site-selective C(sp3)-H functionalizations.
Linear Selective Hydroformylation of 2-Arylpropenes Using Water-Soluble Rh-PNP Complex: Straightforward Access to 3-Aryl-Butyraldehydes
Straightforward access to 3-aryl-butyraldehydes was developed through the aqueous biphasic Rh-catalyzed hydroformylation of 2-arylpropenes using a water-soluble PNP ligand. This protocol accommodates broad substrate scope with high yields (up to 95 %) and excellent linear selectivity (>99 : 1 b/l ratio). The synthesis of rac-ar-turmerone and the gram-scale hydroformylation further demonstrated the practical nature of this method.
Design and application of hybrid phosphorus ligands for enantioselective Rh-Catalyzed anti-markovnikov hydroformylation of unfunctionalized 1,1-disubstituted Alkenes
A series of novel hybrid phosphorus ligands were designed and applied to the Rh-catalyzed enantioselective anti-Markovnikov hydroformylation of unfunctionalized 1,1-disubstituted alkenes. By employing the new catalyst, linear aldehydes with β-chirality can be prepared with high yields and enantioselectivities under mild conditions. Furthermore, catalyst loading as low as 0.05 mol % furnished the desired product in good yield and undiminished selectivity, demonstrating the efficiency of this transformation in large-scale synthesis.