Enantioselective Phospha‐Michael Reaction of Diphenyl Phosphonate with Nitroolefins Utilizing Conformationally Flexible Guanidinium/Bisthiourea Organocatalyst: Assembly‐State Tunability in Asymmetric Organocatalysis

Abstract

A catalytic enantioselective phospha-Michael reaction of diphenyl phosphonate to nitroolefins was achieved by utilizing a 1,3-diamine-tethered guanidinium/bisthiourea organocatalyst. The procedure is applicable to nitroolefins having various aromatic and aliphatic substituents, and enables an efficient access to phospha-Michael products with 90-98% ee. Monomeric or oligomeric active species of the catalyst can be utilized, depending on the presence or absence of water.

1,3‐Diamine‐Derived Bifunctional Organocatalyst Prepared from Camphor

“…In contrast, efficient 1,3‐ and 1,4‐diamine‐derived organocatalysts [with the exception of (BINAM)‐based catalysts] are very rare. Conformationally flexible guanidine‐bisthiourea organocatalysts have been used in asymmetric 1,4‐type Friedel–Crafts reaction of phenols and phospha‐Michael reaction of diphenyl phosphonate with nitroolefins . Ferrocene‐based, and self‐assembled proline‐1,3‐diamine‐thiourea bifunctional organocatalysts showed high enantioselectivity in Michael additions of acetylacetone and aldehydes to nitroolefins.…”

Recent Advances in Chiral Guanidine‐Catalyzed Enantioselective Reactions

“…[43] Nagasawa and Sohtome et al attempted the Michael addition of diphenylp hosphonate to nitroolefins with the help of the conformationally flexible guanidine-thiourea catalyst 7 (Scheme 26). [44] Initial screens of different solvents showed no obvious effect on the enantiomeric preference, but the addition of water as ac o-solvent promoted the enantioselectivity to 95 % ee values. Under optimal reactionc onditions, both aromatic and aliphatic nitroolefins led to corresponding products with excellent enantioselectivity (90-98 % ee values).…”

“…Nagasawa and Sohtome et al. attempted the Michael addition of diphenyl phosphonate to nitroolefins with the help of the conformationally flexible guanidine‐thiourea catalyst 7 (Scheme ) . Initial screens of different solvents showed no obvious effect on the enantiomeric preference, but the addition of water as a co‐solvent promoted the enantioselectivity to 95 % ee values.…”

Enantioselective Synthesis of β‐Nitrophosphonates Using Immobilized Quinine Organocatalyst on Mesoporous SBA‐15 as an Efficient Recyclable Catalyst

“…A substantial amount of research has shown good conversion and enantioselectivities of β‐nitro phosphonate in asymmetric Michael addition of diphenylphosphite to nitroalkenes using bi‐functional organocatalyst . However, high solubility of the catalyst in the reaction medium adversely affects the separation and recyclability of the catalyst.…”