2-Amino-l-indanol

Another chiral titanium reagent, 11, was developed by Corey et al. [17] (Scheme 1.24). The catalyst was prepared from chiral ris-N-sulfonyl-2-amino-l-indanol and titanium tetraisopropoxide with removal of 2-propanol, followed by treatment with one equivalent of SiCl4, to give the catalytically-active yellow solid. This catalyst is thought not to be a simple monomer, but rather an aggregated species, as suggested by NMR study. Catalyst 11 promotes the Diels-Alder reaction of a-bro-moacrolein with cyclopentadiene or isoprene. 

Monochlorotitanium complex 418, prepared from (l/J,25 )-Af-(2,4,6-trimethylbenze-nesulfonyl)-2-amino-l-indanol and titanium tetraisopropoxide followed by treatment with titanium tetrachloride effectively catalyzed the cycloaddition of a-bromoacrolein to cyclo-pentadiene, affording 366 with 93% ee (equation 125)259. Catalyst 418 induced an ee of 90% in the reaction of isoprene with a-bromoacrolein. 

Isomers of ris-l-amino-2-indanol have attracted considerably less attention, although improved asymmetric inductions have been reported on several occasions. Diethylzinc addition to aldehydes with m-.V-disubslil tiled-1 -amino-2-indanols as catalysts yielded secondary alcohols with low enantiomeric excesses (40-50%),37 whereas r/.v-N-disubstituted-2-amino-1 -indanols led to increased selectivities (up to 80% ee) (see Section 17.3.2).46 High degrees of enantioselection were eventually achieved in the addition of diethylzinc to aliphatic and aromatic aldehydes with /raw.v-N-dialkyl-l-substituted-2-amino-l-indanols as catalysts (Scheme 17.25).47 Optimal results were obtained with bulky groups at the hydroxy-bearing carbon and at the nitrogen (R = Ph, R1 = ft-Bu), which led to the formation of (R)-l-phenylpropanol in 90% yield and 93% ee. 

Recently, it was suggested by Corey and coworkers [828] that cis-N-sul-fonyl-2-amino-l-indanols can be used to generate titanium complexes that are able to catalyze the asymmetric cycloaddition of 2-bromoacrolein with dienes. 

This mechanism, however, does not explain the behavior of the other alkenes studied. Thus indene gave two amino alcohols. Only one of them, trans-2-(dimethylamino)-l-indanol, could... 

Table 11.8 Reduction of ketones using 7V-(2-pyridinesulfonyl)-l-amino-2-indanol as a ligand.

Sudo and Saigo153 reported the application of ds-2-amino-3,3-dimethyl-l-indanol derived l,3-oxazolidin-2-one 231 as a chiral auxiliary in asymmetric Diels-Alder reactions. The TV-crotonyl and TV-acryloyl derivatives were reacted with cyclopentadiene, 1,3-cyclohexadiene, isoprene and 2,3-dimethyl-l,3-butadiene, using diethylaluminum chloride as the Lewis acid catalyst. The reactions afforded the expected cycloadducts in moderate to high yields (33-97%) with high endo selectivities and high de values (92% to >98%). 

Encouraged by these successful results, Saigo and co-workers tested ligand 78 in the rhodium-catalyzed hydrosilylation of ketones.56 Indeed, asymmetric hydrosilylation of acetophenone and tetralone using 78 as a chiral source led to considerably improved enantioselectivities (94% and 89% ee, respectively) compared to reactions performed with valinol-derived phosphorous-containing oxazoline 66 (82% and 59%, respectively).59,60 The equal accessibility of the two enantiomers of the m-2-amino-3,3-dimethyl-l-indanol backbone in 78 represented an additional advantage over oxazoline 66, which is derived from an amino alcohol of the chiral pool because (5)-tetralol could easily be obtained using (-)-78 in 97% yield and 92% ee (Scheme 17.30).56... 

Hashimoto et al. [38] reported the synthesis of the P,N oxazoline-containing ligand 59 derived from ds-2-amino-3,3-dimethyl-l-indanol and its application to the intermolecu-lar Mizoroki-Heck reaction. Their best reaction conditions for arylation of various cy-cloalkenes (Scheme 11.23) showed conversions of up to 91% and enantiomeric excesses of up to 98% for the reaction of cyclohexenyl triflate (35) with 2,3-dihydrofuran (1). Reactions using 4,7-dihydro-l,3-dioxepin (46) as the substrate proved less successful, with low conversions of 37% achieved, albeit with high enantiomeric excesses of up to 90%. In all cases, low amounts of isomerization were observed. These results are consistent with, if not better than, many analogous phosphinooxazoline ligands. 

Hashimoto, Y, Horie, Y, Hayashi, M. and Saigo, K. (2000) An efficient phosphorus-containing oxazoline ligand derived from cw-2-amino-3,3-dimethyl-l -indanol application to the palladium-catalyzed asymmetric Heck reaction. Tetrahedron Asymmetry, 11, 2205-10. 

Hydroxy -2-h3rdrindamine (2 - Amino -indanol-l, l-hydroxy-2-aminohydrind )... 

The catalytic system of [Cp RhCl2]2 and (l/ ,25)-(+)-ciiS-l-amino-2-indanol as a chiral ligand achieved the enantioselective synthesis of a-D-benzylalcohols via asymmetric transfer hydrogenation with isopropyl alcohol as the hydrogen source (eq 27). The transformation proceeded smoothly to provide a-D-benzyl alcohols in high yield, albeit in moderate enantioselectivity. 

In contrast to tran -selectivity (cndo-selectivity) of the Ni (n)-catalyzed reactions, Sibi et al. reported ciiy-selective (exo-selective) and highly enantioselective cycloadditions between -cyclic azomethine imines and 2-acryloyl-l-benzyl-5,5-dimethyl-3-pyrazohdinone catalyzed by the bisoxazoline-Cu(II) complex (10mol%) consisting of Cu (OTf>2 and (15,2I )-l-amino-2-indanol-deiived bisoxazoline (INDABOX) (Table 7.2) [12]. Interestingly, the use of additional chiral Lewis acid complexes prepared from INDABOX and Mg(II), Zn(II), or Ni(II) salts led to tmns-selective (emio-selective) cycloadditions of azomethine imine. The INDABOX-Mg(OTf)2- and INDABOX-Zn... 

Both enantiomers of (Z)-l-amino-2-indanol are available commercially. 

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