Accelerated and Enantioselective Synthesis of a Library of P‐Stereogenic Urea Phosphines

• Published in: European journal of organic chemistry 2018-12, Vol.2018 (47), p.6768-6779
• Main Authors: Koshti, Vijay S., Gote, Ravindra P., Chikkali, Samir H.
• Format: Article
• Language: English
• Subjects: Asymmetric catalysis; Catalysis; Chemical synthesis; Enantiomers; Functional groups; Ligands; NMR; Nuclear magnetic resonance; Palladium catalyst; Phosphines; Phosphorus; Phosphorus compounds; P‐C coupling; P‐Ligands; Spectroscopic analysis; Urea phosphines; Ureas
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201801309

Chiral phosphorus ligands play a central role in majority of the asymmetric transformations. However, access to chiral phosphorus ligands is limited due to their challenging synthesis. Reported here is a highly efficient and accelerated catalytic asymmetric synthesis of P‐stereogenic urea containing phosphines leading to a small library of 18 chiral phosphorus compounds. Characteristic two doublets in a 31P NMR spectrum, spectroscopic and analytical evidences authenticated the formation of [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] complex. Indeed, [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] was found to catalyze the C‐P coupling reaction and quantitative conversion was observed within 18 hours. Under optimized conditions, iodophenyl urea's (2a–2j) were treated with secondary phosphines (1a–1c) in presence of [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] to obtain P‐stereogenic urea phosphines 5a–5r. The identity of these urea derived phosphines was unambiguously ascertained using a combination of spectroscopic and analytical methods. The catalyst tolerated various functional groups and yielded corresponding urea containing phosphines with an enantiomeric excess in the range of 15–62 %. Reported here is a highly efficient and accelerated catalytic asymmetric synthesis of P‐stereogenic urea phosphines leading to a small library of 18 P‐chiral phosphorus compounds. The de novo [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] catalyst tolerated various functional groups and furnished corresponding urea substituted phosphines with an enantiomeric excess of up to 62 %.