Chiral BINOL-derived phosphoric acids

In 2008, Toste and coworkers reported the desymmetrization of me o-episulfonium ions 131 generated in situ from ring closure of sulfides 132 featuring a P-trichloro-acetimidate leaving group [76], Chiral BINOL-derived phosphoric acid (5)-3o (15 mol%, R = triggered the formation of the intermediate mera-epi-... 

A chiral Lewis acid catalyst was prepared between the chiral BINOL-derived phosphoric acid (212) and Et2AlCl. In the presence of a catalytic amount of the A1 complex, the reaction between (i )-isocyanoacetamides (209) and aldehydes (210) afforded the corresponding enantio-enriched 2-(l-hydroxyalkyl)-5-aminooxazoles (211) in good yields and enantioselectivities (Scheme 59). ... 

Br0nsted Acid Organocatalysis. The field of Brpnsted add organo-catalysis [151] is clearly dominated by chiral binol-derived phosphoric acids, which after the seminal reports of Akiyama et al. [152] and of Uraguchi and Terada [153] have become one of the most powerful types of organic catalysts [154]. Figure 2.33... 

FIGURE 2.33. Chiral binol-derived phosphoric acids. 

It worth to mention that despite the importance of the Kabachnik-Fields reaction, stereoselective versions for the synthesis of enantioenriched a-aminophosphonates are scarce [212, 213], and only few enantioselective examples have been published to date (for reviews on enantioselective catalytic direct hydrophosphonylations of imines, see Refs. [162a-c]). Organocatalytic examples use well-known chiral binol-derived phosphoric acid organocatalysts (Fig. 12.6,80 and 81) [214], and regarding metal catalysis, chiral scandium(III)-A,A -dioxide and... 

Thus, in 2008, List and coworkers published the first enantioselective version of Kabachnik-Fields reaction [214a]. They found that chiral binol-derived phosphoric acids were efficient in inducing chirality under dynamic kinetic resolution conditions when bulky a-branched aldehydes (isopropyl, cyclopentyl and cyclohexyl) were used as substrate in their reaction with p-anisidine and di(3-pentyl) phosphite (Scheme 12.28). In particular, 3,3 -bis(4-anthracenyl-2,6-diisopropylphenyl)-l,l -8-binaphtyl-2, 2 -diyl hydrogenphosphate 80 allowed the synthesis of the corresponding p,p-disubstituted-a-aminophosphonates 84 in high yields with very good stereocontrol (dr up to 28 1 and er up to 97 3). 

SCHEME 12.28 Enantioselective Kabachnik-Fields reaction catalyzed by chiral binol-derived phosphoric acid 80. 

An a/ -stereo- and diastereo-selective glycosylation method employs a glucosyl a-trichloroacetimidate and a chiral BINOL-derived phosphoric acid catalyst the system selects the i -enantiomer of a racemic mixture of secondary alcohols. ... 

Strained allylic cyclobutanols and cyclopropanols undergo ring expansion promoted by a chiral binol-derived phosphoric acid catalyst to give 0-fluoro spiroketone products (Scheme 80). ... 

Later, these authors reported the utilisation of a combination of Rh2(OAc)4 with a chiral BINOL-derived phosphoric acid to induce an enantioselective three-component Mannich-type reaction of diazo compounds, carbamates and imines, providing a rapid and efficient access to... 

Later, You et al. investigated relay catalysis consisting of a combination of the same ruthenium catalyst and a closely related chiral BINOL-derived phosphoric acid. As shown in Scheme 7.42, the use of this catalyst system in an asymmetric domino intramolecular Friedel-Crafts-type-aza-Michael reaction allowed a range of chiral fused indoles to be achieved in high yields and moderate to high enantioselectivities from the corresponding enones and indolyl olefins. 

At almost the same time, Akiyama et al. developed a similar aza-Darzens reaction using aldimines derived from aryl glyoxals and ethyl diazoacetate promoted by chiral BINOL-derived phosphoric acid catalysts, such as 90 (Scheme 37.17) [159]. In this case, the reaction rendered exclusively the corresponding cis-aziridine carboxylates in both excellent yields (95-100%) and enantioselectivities (92-97% ee). However, the scope of the method seemed to be quite narrow since only aromatic glyoxals were employed. 

In 2004, Akiyama s and Terada s groups independently pioneered the development of chiral BINOL-derived phosphoric acids 197, which have subsequently found wide resonance as catalysts in various asymmetric transformations [33, 41, 42]. Akiyama reported that silyl ketene acetals such as 237 participate in additions to aromatic aldimines with high diastereo- and enantioselectivity in the presence of catalyst 238 (Equation 21) [146]. In parallel studies, Terada demonstrated that the chiral phosphoric acid 242 readily catalyzes direct asymmetric Mannich reactions between acetylacetone (241) and N-Boc-protected aromatic aldimines such as 240 (Equation 22) [145]. 

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