Binaphthyl derivative organocatalysts

Currently, the chiral phase-transfer catalyst category remains dominated by cinchona alkaloid-derived quaternary ammonium salts that provide impressive enantioselec-tivity for a range of asymmetric reactions (see Chapter 1 to 4). In addition, Maruoka s binaphthyl-derived spiro ammonium salt provides the best results for a variety of asymmetric reactions (see Chapters 5 and 6). Recently, some other quaternary ammonium salts, including Shibasaki s two-center catalyst, have demonstrated promising results in asymmetric syntheses (see Chapter 6), while chiral crown ethers and other organocatalysts, including TADDOL or NOBIN, have also found important places within the chiral phase-transfer catalyst list (see Chapter 8). 

Vishnumaya and Singh developed a highly efficient water-compatible binaphthyl derived diamine organocatalyst Ih and successfully used it in asymmetric Michael reactions. The treatment of ketones with both aryl and allgrl nitro-olefins afforded the desired products with high to excellent stereoselectivities (Scheme 9.16). The Chen group used the bicyclic... 

Binaphthyl-derived Cyclic Amines and Their Salts as Asymmetric Organocatalysts... 

In 2005, Wang and coworkers reported a new bifunctional binaphthyl-derived amine thiourea 16 as an efficient organocatalyst for the Morita-Baylis-Hillman reaction of cyclohexenone with aliphatic, aromatic and sterically hindered aldehydes. The design of the catalyst follows Takemoto s design of a bifunctional motif. This catalytic protocol provided access to useful chiral allylic alcohol building blocks in high yields and high enan-tioselectivities (Scheme 19.21). 

Other chiral Bronsted acid organocatalysts developed more recently include chiral binaphthyl-derived disulfonic acids [162] and sulfonimides [163] and SPINOL-derived phosphoric acids [164]. 

A new class of suitable optically active organocatalyst for enantioselective alkylations has recently been developed by Maruoka and co-workers [le, 33-37]. This catalyst is not based on an alkaloid-related quaternary ammonium salt but consists of a C2 -symmetric compound of type 29 (or derivatives thereof bearing other types of substituent on the 3,3 positions of the binaphthyl unit) [33, 34], In the presence... 

Jurczak and co-workers reported hybrid diamines derived from l,r-binaphthyl-2,2 -diamine and a-amino acids as organocatalysts for 1,3-dipolar cycloaddition of aromatic nitrones 187 to ( )-crotonaldehyde 28b, Scheme 3.62 [79]. The L-phenylalanine-based l,r-binaphthyl-2,2 -diamine (BINAM) catalyst 194, with trifluoromethanesulfonic acid as an additive, afforded the optimal results with good endo-diastereoselectivity and enantioselectivity up to 95% ee. 

In 2010, Enders et al. reported on an organocatalytic, one-pot, three-component reductive amination/aza-Michael sequence. They used bis(2,4,6-triisopropyl-phenyl)-l,l -binaphthyl-2,2 -diyl hydrogenphosphate (TRIP) 319 as the organocatalyst and 2-binaphthyl substituted benzathioazole derivatives 320 as the reducing agent and t-BuOH was used as the base. After alkylative cyclization, substituted tetrahydroisoquinoline derivatives 318 were formed in high yields with excellent stereoselectivity (Scheme 40.69). 

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