Planar chiral [2.2]paracyclophane-based phosphine-Brønsted acid catalysts bearing exceptionally high reactivity for aza-Morita–Baylis–Hillman reaction

Applications of Chiral Phosphine‐Based Organocatalysts in Catalytic Asymmetric Reactions

“…Recently, Kitagaki et al. synthesized several planar chiral bifunctional phosphine compounds ( 61 ) based on the [2.2]paracyclophane backbone with a pseudo‐ ortho ‐substitution pattern and applied them in the aza‐MBH reaction 40. An enantiopure phosphine‐phenol catalyst, ( S p )‐ 61 c , which contained an aryl group as a spacer connected to a phosphino group, exhibited exceptionally high reactivity, thus affording the corresponding adducts ( 62 ) in high yield with good enantioselectivities (up to 99 % yield, 85 % ee ; Scheme ).…”

Enantiopure planar chiral [2.2]paracyclophanes: Synthesis and applications in asymmetric organocatalysis

“…85 In addition to PhanePhos and its derivatives, planar chiral pCp-based bifunctional phosphine-phenol compounds have been prepared and used as catalysts in metal-free reactions (Scheme 23). [86][87][88][89] To access these compounds, 4-bromo-12-hydroxy[2.2] paracyclophane (S p )-47 is first isolated through a mono metalation of enantiomerically pure 4,12-dibromo[2.2]paracyclophane (S p )-21, followed by a reaction with trimethylborate, and oxidation of the resulting product with hydrogen peroxide and sodium hydroxide. The obtained key intermediate (S p )-47 is then engaged into a Suzuki-Miyaura coupling in the presence of phosphinylboronic esters.…”

“…87 Bifunctional phosphine-phenol pCp derivatives such as compound (S p )-49 have been employed to catalyze asymmetric aza-Morita-Baylis-Hillman reactions of aldimines with vinyl ketones (Scheme 24). 88,89 The same catalysts can also be used to promote enantioselective [3 + 2] annulations of unsubstituted allenic esters and N-tosylimines (Scheme 24). 86 In both transformations, bifunctional pCps provide better yields and enantioselectivities in comparison with PhanePhos or other planar chiral ligands.…”

Asymmetric Reactions Catalyzed by Chiral Tertiary Phosphines

“…Kitagaki and co‐workers synthesized several new planar chiral bifunctional phosphines 6 based on the [2.2]paracyclophane backbone with a pseudo‐ortho substitution pattern and applied them in the aza‐MBH reaction. [ 7 ] An enantiopure phosphine‐phenol catalyst ( S p )‐ 6c bearing an aryl group as a spacer connected to a phosphino group exhibited an exceptionally high reactivity, affording the corresponding aza‐MBH adducts 7 in high yield with good enantioselectivity (up to 99% yield, 85% ee) (Scheme 2). Štěpnička and co‐workers recently reported the preparation and structural characterization of a series of new chiral ferrocenophane phosphines 8 .…”