BINOL phosphoric acid

Simon L, Goodman JM (2008) Theoretical study of the mechanism of Hantzsch ester hydrogenation of imines catalyzed by chiral BINOL-phosphoric acids. J Am Chem Soc 130 8741-8747... 

An enantioselective Strecker reaction involving Brpnsted acid catalysis uses a BINOL-phosphoric acid, which affords ees up to 93% in hydrocyanations of aromatic aldimines in toluene at -40 °C.67 The asymmetric induction processes in the stereoselective synthesis of both optically active cis- and trans-l-amino-2-hydroxycyclohexane-l -carboxylic acids via a Strecker reaction have been investigated.68 A 2-pyridylsulfonyl group has been used as a novel stereocontroller in a Strecker-type process ees up to 94% are suggested to arise from the ability of a chiral Lewis acid to coordinate to one of the sulfonyl (g)... 

Several chiral catalysts for conjugate addition have been explored, including both protic and Lewis acids. 3,3 -hri-(4-Nitrophenyl)-BINOL-phosphoric acid gives 40-98% yields and 40-55% ee with p-aryl enones [243]. 

The chiral catalysts that have been used in nitroaUcene conjugate additions include bw-oxazolines with Cu(OTF)2 [281] or Zn(OTf)2 [282], tridentate bw-oxazolines with Zn(OTf)2 [283], mixed thiazoline-oxazolines with Zn(OTf)2 [284], imidazoUne-aminophenols with CuOTf [285], bis-trifluoromethylsulfonamides [286], binaphthyl sulfonamides [287], binaphthyl imines [288], thioureas [289], and quinoUnyl thioureas [290]. A BINOL-phosphoric acid with 3A molecular sieves gave ee values consistently at 90% and above with both p-alkyl and p-aryl nitroalkenes [291]. 

A related reaction involves the use of aryl indole-3-carbinols with enamides. Under the influence of acid catalysts the carbinols generate electrophiles. The adducts hydrolyze to products that are the equivalent of conjugate addition to 1,3-diaryl propenones. These reactions can be done in up to 90% ee with chiral BINOL-phosphoric acid catalysts [293]. 

The cyclization of 103-A exhibits some enantioselectivity when conducted with a BINOL-phosphoric acid [295]. 

Excellent enantioselectivity has also been obtained using 3,3 -6 s-(l-naphthyl) BINOL-phosphoric acids [311]. A -Tosyl imines of aryl aldehydes were also examined using a binaphthyl Pd(II) carbene complex as the catalyst. Enantioselectivity in the 50-75% range was obtained [312]. Imines formed from ot-phenylethylamine and ethyl 3,3,3-trifluoropyruvate give adducts with 85-97% de in the presence of TEA [313]. The chiral auxiliary can be removed by hydrogenolysis. 

Highly substituted BINOL-phosphoric acids give good (70-95%) enantio-selectivity with (iw-(ethoxycarbonyl)tryptamines but tryptamine itself is unreactive [344]. 

BINOL-phosphoric acids have been used successfully with N-substimted tryp-tamines [345], The chiral acid catalysis of the Pictet-Spengler cyclization has been applied to alkaloid synthesis, as in the case of ( )-arboricine [346]. 

Calculations suggested that the Strecker reaction of iV-aryl imines catalyzed by the BINOL-phosphoric acid catalyst (124) proceeded through transition states in which the catalyst simultaneously bound both the imine and the nucleophile (Scheme 35). ... 

Scheme 16.34). Thus, reaction of tryptamine derivatives with either enol lactones [69] or ketoacids [70] in the presence of catalytic amounts of binol phosphoric acids afforded tetracyclic products in high yields and good to excellent... 

Later on, the Rueping group reported an organocatalytic enantioselective reduction of pyridine 180 (Scheme 17.30) [74], according to the procedure described by Bohlmann and Rahtz [75]. The key step in the synthesis of decahydroquinolines from the pumiliotoxin family involved Hantzsch dUiydropyridine 172 as the hydride source and involved BINOL-phosphoric acid 181 as a chiral Br0nsted acid catalyst... 

Similarly, using BINOL phosphoric acid catalyst 191, Hiemstra and co-workers developed an organocatalytic Pictet-Spengler (PS) reaction of tryptamine derivative 189 and 4 -oxo-pentanal 190 as a key step to achieve the key intermediate 192 (86% yield, 89% ee), which was then converted to (—)-arboricine (193) [78] by a sequence of reactions including diasteroselective Pd(0)-catalyzed iodoalkene-enolate cycUza-tion (33% overall yield, 6 steps) (Scheme 17.32) [79]. Importantly, only 1 mol% loading of catalyst 191 on a 10 mmol Pictet-Spengler (PS) reaction scale gave the compound 192 in 92% yield, but with relative low enantioselectivity (78% ee). 

Sewgobind NV, Wanner MJ, Ingemann S, de Gelder R, van Maarseveen JH, Hiemstra H (2008) Enantioselective BINOL-Phosphoric Acid Catalyzed Pictet-Spengler Reactions of N-Benzyltryptamine. J Org Chem 73 6405... 

A hydroamination/N-sulfonyliminium cyclization cascade was carried out enantioselectively with gold and BINOL-phosphoric acid catalysts to generate fused indole 188. The method can also be extended to furnish lactams with up to 93% ee (13OL4330). Polycyclic indoline 189 was prepared via an indium/TFA-catalyzed tandem cycloannulation of P-oxodithioesters with tryptamine in yields up to 92% (130L1974). Dixon and colleagues utilized an enantioselective Michael addition/iminium ion cyclization of trypt-amine-derived ureas in the synthesis of tetracyclic indole 190 (22 examples, up to 78% yield and 96% ee) (130L2946). 

The good enantio- and regioselectivity can be explained through transition state TS-6 where the azomethine ylide and the methyleneindolinone build hydrogen bonds with the chiral BINOL-phosphoric acid catalyst 239 (Fig. 6.10). 

DFT has been employed to probe the mechanisms of chiral BINOL-phosphoric-acid-catalysed allylboration and propargylation reactions, with a particular focus on whether the catalyst interacts with the pseudo-axial or pseudo-equatorial oxygen of the boronate. °... 

Enantioselective versions of the Hantzsch reaction have also been reported. As shown in Scheme 3.2, the reaction between dimedone, ethyl acetoacetate, ammonium acetate, and aromatic aldehydes in the presence of a chiral BINOL-phosphoric acid catalyst 7 gave compounds 8 in good to excellent yields and in enantiomeric excesses above 94%, although the absolute configuration of the final products was not determined [10]. 

In the second reaction, a Michael-Michael cascade between an unsaturated oxin-doles 17 and enones 22 was shown to be catalyzed by a primary amine-derived catalyst (II) (Scheme 10.3). The reaction afforded the spirooxindoles 23 in excellent yields and diastereo and enantioselectivities. Wang used a similar approach in the reaction of isatylidene malononitriles and enones [12]. The reaction was catalyzed by the dual combination of cinchona-based chiral primary amine and BINOL phosphoric acids to afford the spirocycles in excellent yields (88-99%), diastereo (up to 99 1 dr), and enantioselectivities (95-99% ee). 

The effective and unprecedented chiral BINOL phosphoric acid (263) catalysed dearomatisation of indoles (261) through electrophilic activation of allenamides (262) has been reported by Bandini et al. (Scheme 70). ... 

For comprehensive mechanistic investigations regarding imine reactions catalysed by chiral BINOL-phosphoric acids see ... 

A purely ionic hydrogen bond activation mechanism might be involved in the aza-Henry reaction between a-iminoesters, a very reactive subclass of imines, and various nitroalkanes catalyzed by the BINOL phosphoric acid 44 [54]. The corresponding P-nitro-a-amino acid esters were produced in good yields, diastereo- and enantioselectivities (Scheme 29.23). The authors postulated a dual role of catalyst 44 through activation of the a-iminoester by protonation and control over the nitroaUcane/nitronate equilibrium (Scheme 29.24). 

A two-step route for the synthesis of 3,3 -disubstituted and 6,6 -dis-ubstituted chiral BINOL phosphoric acids (50) has been realised via the Suzuki coupling involving brominated BINOL phosphoric acids (49) (Scheme 10). ... 

Chiral BINOL phosphoric acids (253) catalysed asymmetric reaction of A -acyl imines (295) with thiols (296) to give enantioenriched A, S-acetals (297) in excellent yields (Scheme... 

The combination of a cinchona-based chiral primary amine (304) and a BINOL-phosphoric acid (305) has been demonstrated as a powerful catalytic system for the double Michael addition of isatylidene malononitriles (301) with P-unsaturated ketones (302), to provide the novel chiral spiro-[cyclohexane-l,3 -indoKne]-2, 3-diones (303) in high yields (88-99%) with excellent diastereo- and enantioselectivities (94 6-99 1 dr, 95-99% ee) (Scheme 79). ... 

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