Three different bile acid-derived biphenyl phosphites were synthesized, starting from cholic and deoxycholic acids and biphenol, and their stereochemical features were checked by CD and NMR spectroscopies. On the basis of the spectroscopic results, the capability of the cholestanic system to induce a prevalent sense of twist on the biphenyl moiety of the bile acid-derived phosphites as well as their tropos nature was inferred.

The chemoselective reduction of commercial‐grade aldehydes (97–99 %) to primary alcohols is achieved with cis‐[RuCl2(ampy)(PP)] [ampy=2‐(aminomethyl)pyridine; PP=1,4‐bis(diphenylphosphino)butane, 1,1′‐ferrocenediyl‐bis(diphenylphosphine)] and pincer [RuCl(CNNR)(PP)] [PP=1,3‐bis(diphenylphosphino)propane, 1,4‐bis(diphenylphosphino)butane, 1,1′‐ferrocenediyl‐bis(diphenylphosphine); HCNNR=4‐substituted‐2‐aminomethyl‐benzo[h]quinoline; R=Me, Ph] complexes by transfer hydrogenation and hydrogenation reactions. Aromatic, conjugated, and aliphatic aldehydes are converted quantitatively to the corresponding alcohols using 2‐propanol with potassium carbonate at substrate/catalyst ratios up to 100 000 by transfer hydrogenation, whereas aldehyde hydrogenation (5–20 atm of H2) is achieved efficiently in MeOH in the presence of KOtBu at substrate/catalyst ratios up to 40 000.

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Reaction of 1-naphthylamine with ethyl benzoylacetate gives the corresponding benzoyl acetamide derivative 1, which undergoes cyclization to 4-phenylbenzo[h]quinolin-2(1H)-one (2) in the presence of H2SO4. Bromination with POBr3, followed by reaction with n-BuLi and DMF, gives 4-phenylbenzo[h]quinoline-2-carbaldehyde (4), which is converted to the corresponding oxime hydrochloride 5 with NH2OH·HCl. Hydrogenation of 5 catalyzed by 10% Pd/C (type 338) leads to 4-phenyl-2-aminomethylbenzo[h]quinoline hydrochloride (HCNNPh·HCl, 6) isolated in high yield. Similarly, the 4-methyl-2-aminomethylbenzo[h]quinoline derivative (HCNNMe·HCl, 12) is prepared starting from 1-naphthylamine and 2,2,6-trimethyl-4H-1,3-dioxin-4-one, following the route for 6. Reaction of RuCl2(PPh3)3 with a diphosphine (PP), the HCl salt 6, and NEt3 in 2-propanol leads to the pincer complexes RuCl(CNNPh)(PP) (PP = Ph2P(CH2)3PPh2, 13; Ph2P(CH2)4PPh2, 14; 1,1′-bis(diphenylphosphino)ferrocene, 15). The methyl derivatives RuCl(CNNMe)(PP) (PP = Ph2P(CH2)3PPh2, 16; Ph2P(CH2)4PPh2, 17; 1,1′-bis(diphenylphosphino)ferrocene, 18) are obtained in a similar way using 12 in place of 6. Treatment of [RuCl2(p-cymene)]2 with rac-BINAP, 6, and NEt3 affords RuCl(CNNPh)(BINAP) (19), isolated as a mixture of two diastereoisomers (3:4 molar ratio). The chiral RuCl(CNNPh)[(S,R)-JOSIPHOS] (20) is obtained as a single isomer from [RuCl2(p-cymene)]2, (S,R)-JOSIPHOS, and 6. Complexes 13-20 efficiently catalyze the transfer hydrogenation of acetophenone in 2-propanol at reflux in the presence of NaOiPr (2 mol%) with S/C = 5000-20-000 and at high rate (TOF up to 6.7 × 103 min-1). With complexes 13, 15, 17, and 18 several ketones of commercial-grade purity have been reduced to alcohols, including the bulky RCO(tBu) (R = Me, Ph) substrates. With 20 acetophenone is reduced to (S)-1-phenylethanol with 85% ee. The pincer complexes 13-15 and 18 are also found highly active in the hydrogenation of ketones at 40 °C with an S/C = 10-000, under 5 bar of dihydrogen in methanol and in the presence of 2 mol % of a base (NaOH, KOH, NaOMe)

Different tropos deoxycholic acid derived biphenylphosphites were used as Rh(I) chiral ligands, at P/Rh 1:1 and 2:1 molar ratios, to obtain mono-or disubstituted Rh(I) complexes, which act as catalytic precursors in the asymmetric conjugate addition of arylboronic acids to cyclic enones, giving the addition products in high to quantitative yields and ee's up to 92%. In addition, using an excess of arylboronic acid only the disubstituted complexes gave diastereomerically pure 1,3-diarylcyclohexanols with ee's up to 94%. The tropos nature of the complexes, as well as the coordination mode, was investigated by 31 P NMR spectroscopy. A disubstituted rhodium complex was isolated, and its X-ray molecular structure was determined.

Different deoxycholic acid derived biphenylphosphites, whose tropos nature was ascertained by NMR and CD measurements, were used in the rhodium-catalyzed asymmetric hydrogenation of dimethylitaconate achieving enantiomeric excesses up to 91%. The comparison of these results to those obtained using the corresponding atropoisomeric binaphthyl analogues, together with NMR and CD measurements on the rhodium complexes of some phosphites, allowed us to shed light on the nature of the active catalytic species and on the asymmetric induction process and hence to recognize the most appropriate stereochemical features to reach good levels of enantioselectivity.

Using the deoxycholic acid derived tropos biphenylphosphite as a Rh(i) chiral ligand different complexes are obtained, depending on the Rh : L molar ratio, that give rise to the formation of different chiral products in the asymmetric addition of phenylboronic acid to cyclohexenone.

Aldehydes were chemoselectivelyr educed to primary alcohols by using HCOONH 4 as the hydrogen donor throught ransfer hydrogenation catalyzed by benzo [h]quinoline pincer complexes RuCl(CNN Ph )(PP) at substrate to catalystm olar ratios of 2000 to 20 000. This practical reaction performed with aldehydes of commercial-grade purity in aw ater/tolueneb iphasic system afforded alcohols without the formation of condensation or amination side products.The search of well-designed and productive catalysts for the selectiveh ydrogenation [1] and transfer hydrogenation (TH) [2] of aldehydes to primary alcohols is af undamentalr eactiono f broad application in industry. [3] This catalytic route promoted by transition metals results in al ower environmental impact and an easier workup with respect to the classical approach entailing NaBH 4 ,L iAlH 4 ,b oranes, and Al alkoxides as reducing agents. [4] Among the transition metalsu sed in catalytic homogeneousr eductions,r uthenium,w hichi sc heaper than rhodium and iridium,h as played ac rucial role, and this has led to an umber of efficient catalysts for aldehyde reduction by using H 2 under pressure [5] or 2-propanol. [5e, 6] Whereas the TH with 2propanol is an equilibrium reactiont hat, on scale, requires the removalo fa cetone to drivet he reaction to completion, the use of formic acid derivatives as hydrogen donors has the advantageo fg enerating CO 2 ,w hich is released from the reaction solution,a nd this drives the reaction and minimizesr eversibility problems. [7] Alkali formates HCOOM (M = Na, K) have been employed in the TH of aldehydes with RuCl 2 (PPh 3 ) 3 , [8] [RuCl 2 (mtppms) 2 ] 2 (mtppms = sodium 3-diphenylphosphinobenzenesulfonate), [9] CpRuCl(PPh 3 )(PN) (Cp = h 5 -cyclopentadienyl;P N = diphenyl-2-pyridylphosphine), [10] RuCl 2 (PTA) 4 (PTA = 1,3,5-triaza-7-phosphaadamantane), [11] and RuCl 2 (PO) 2 [PO = (2-methoxyethyl)diphenylphosphine] [12] catalysts at substrate to catalystm olar ratios (S/C) 1000, whereas the HCOOH-NEt 3 system has been used with Ru-arenec omplexes, but at al ow S/C = 50-200. [13] Ammonium formate is ac heap and readily accessible reducing agent widely employed in organic transformations. In addition to the Leuckart-Wallach reductive amination of carbonyl compounds, [14] metal-catalyzed versions of this reactionw ere reported by Kitamura [15] and Ta lwar [16] with Cp*R h III (Cp* = h 5pentamethylcyclopentadienyl) and Ir III complexes, respectively, whereas Kadyrov described the asymmetric version with RuCl 2 [(R)-Tol-BINAP][(R)-Tol-BINAP = (R)-(+)-2,2'-bis(di-4-tolylphosphino)-1,1'-binaphthyl]. [17] HCOONH 4 has also been widely used in the Pd/C-catalyzed conversion of carbonyl compounds into alkanes, [18] nitro derivatives into amines [19] and in the hydrodehalogenation of aromatic chlorides. [20] For the employment of HCOONH 4 in the TH of carbonyl compounds, Grainger [21] recently described the use of Wills' tethered Ru complexesi nt he reduction of ketones,w hereas Nie [22] observed the concomitant TH and reductive aminati...