A New Class of 3′‐Sulfonyl BINAPHOS Ligands: Modulation of Activity and Selectivity in Asymmetric Palladium‐Catalysed Hydrophosphorylation of Styrene

Abstract

Palladium-catalysed monophosphorylation of (R)-2,2'-bisperfluoroalkanesulfonates of BINOL (R F = CF 3 or C 4 F 9 ) by a diaryl phosphinate [Ar 2 P(O)H] followed by phosphine oxide reduction (Cl 3 SiH) then lithium diisopropylamide-mediated anionic thia-Fries rearrangement furnishes enantio-Coupling of (R)-8a-j with (S)-1,1'-binaphthalene-2,2'-dioxychlorophosphine (S)-9 generates 3'-sulfonyl BINAPHOS ligands (R,S)-10a-j in good yields (43-82%). These new ligands are of utlility in the asymmetric hydrophosphonylation of styrene (1) by 4,4,5,5-tetramethyl-1,3,2-dioxaphospholane 2-oxide (2), for which a combination of the chiral ligands with either [Pd(+ /NaCHA C H T U N G T R E N N U N G (CO 2 Me) 2 proves to be a convenient and active pre-catalyst system. A combination of an electron-rich phosphine moiety and an electron-deficient 3'-sulfone moiety provides the best enantioselectivity to date for this process, affording the branched 2-phenethenephosphonate, (À)-iso-3, in up to 74% ee with ligand (R,S)-10i, where Ar = panisyl and the 3'-SO 2 R group is triflone.

Recent Advances in Metal-Catalyzed C–P Bond Formation

“…For example, up to 74% ee for the favored branched isomer was observed with a Pd(Binaphos) catalyst (Scheme 14) [23,24]. P-H bonds in H-phosphonates and secondary phosphine oxides could also be added to special alkene derivatives, cyclopropenes, with Pd catalysts [25].…”

Recent Progress in Transition Metal-Catalyzed Addition Reactions of H–P(O) Compounds with Unsaturated Carbon Linkages

“…Since palladium-catalyzed hydrophosphorylation of styrene with pinacol phosphonate is exceptionally branched-selective, its asymmetric version has attracted a special interest (Scheme 50) [54][55][56]. Among the ligands screened, BINAPHOS 32 used in conjunction with CpPd( 3 -allyl) displays better performance (branched/linear ¼ 93/7, 56% ee).…”

3,3′-Bis(trifluoromethanesulfonyl)-2,2′-dihydroxy-1,1′-binaphthalene

“…3 Both compounds gave good product yields, but the title compound gave poor enantioselectivity (10% ee), and the mono-triflone analog gave moderate enantioselectivity (44% ee) in an initial substrate screen. 4 Analogs of BINAPHOS 9 have been prepared from BINOL-2,2bistriflate in a sequence that includes a thia-Fries rearrangement (eq 4). 4 Further functionalization of the ligands can be achieved by substituting the CF 3 of the triflone group with Grignard reagents.…”

“…4 Analogs of BINAPHOS 9 have been prepared from BINOL-2,2bistriflate in a sequence that includes a thia-Fries rearrangement (eq 4). 4 Further functionalization of the ligands can be achieved by substituting the CF 3 of the triflone group with Grignard reagents. Some of the sulfonated BINAPHOS analogs reported gave higher activity and branched (iso-) product ee in Pdcatalyzed hydrophosphorylation than the parent BINAPHOS ligand (up to 74%) (eq 5).…”