About Dendrimers: Structure, Physical Properties, and Applications

Hydrogenation is a core technology in chemical synthesis. High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center. This catalyst system allows for the preferential reduction of a C=O function over a coexisting C=C linkage in a 2-propanol solution containing an alkaline base. The hydrogenation tolerates many substituents including F, Cl, Br, I, CF(3), OCH(3), OCH(2)C(6)H(5), COOCH(CH(3))(2), NO(2), NH(2), and NRCOR as well as various electron-rich and -deficient heterocycles. Furthermore, stereoselectivity is easily controlled by the electronic and steric properties (bulkiness and chirality) of the ligands as well as the reaction conditions. Diastereoselectivities observed in the catalytic hydrogenation of cyclic and acyclic ketones with the standard triphenylphosphane/ethylenediamine combination compare well with the best conventional hydride reductions. The use of appropriate chiral diphosphanes, particularly BINAP compounds, and chiral diamines results in rapid and productive asymmetric hydrogenation of a range of aromatic and heteroaromatic ketones and gives a consistently high enantioselectivity. Certain amino and alkoxy ketones can be used as substrates. Cyclic and acyclic alpha,beta-unsaturated ketones can be converted into chiral allyl alcohols of high enantiomeric purity. Hydrogenation of configurationally labile ketones allows for the dynamic kinetic discrimination of diastereomers, epimers, and enantiomers. This new method shows promise in the practical synthesis of a wide variety of chiral alcohols from achiral and chiral ketone substrates. Its versatility is manifested by the asymmetric synthesis of some biologically significant chiral compounds. The high rate and carbonyl selectivity are based on nonclassical metal-ligand bifunctional catalysis involving an 18-electron amino ruthenium hydride complex and a 16-electron amido ruthenium species.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1521-3773%2820010105%2940%3A1%3C40%3A%3AAID-ANIE40%3E3.0.CO%3B2-5

Asymmetric Catalysis by Architectural and Functional Molecular Engineering: Practical Chemo‐ and Stereoselective Hydrogenation of Ketones

Recent Advances in the Baylis−Hillman Reaction and Applications

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

Large-scale applications of transition metal-catalyzed couplings for the synthesis of pharmaceuticals.

Optically active β-(tert-hydroxy)esters with good enantiomeric excesses (up to 75% e.e.) are synthesised via enantioselective Reformatsky reaction with ketones in the presence of chiral N,N-dialkylnorephedrine.

Enantioselective Reformatsky Reaction with Ketones. Asymmetric Synthesis of β‐(tert‐Hydroxy) Esters.

A new and efficient one-pot system of asymmetric catalysis is presented in which a chiral catalyst (5-pyrimidyl alkanol) self-improves its ee by asymmetric autocatalysis and then acts as a highly enantioselective chiral catalyst for other asymmetric synthesis (addition of dialkylzincs to aldehydes) to provide products (sec-alcohols) with very high ee (up to 99%).

Asymmetric Synthesis with a Chiral Catalyst Generated from Asymmetric Autocatalysis.

Asymmetric Synthesis of 3-Quinolylalkylamine by Enantioselective Alkylation of N-Diphenylphosphinyl-3-quinolylimine Using Chiral β-Amino Alcohols.

(1; R = Me) [552-79-4] C11H17NO (MW 179.29)

InChI = 1S/C11H17NO/c1-9(12(2)3)11(13)10-7-5-4-6-8-10/h4-9,11,13H,1-3H3/t9-,11-/m0/s1

InChIKey = FMCGSUUBYTWNDP-ONGXEEELSA-N

(2; R = n-Bu) [115651-77-9] C17H29NO (MW 263.47)

InChI = 1S/C17H29NO/c1-4-6-13-18(14-7-5-2)15(3)17(19)16-11-9-8-10-12-16/h8-12,15,17,19H,4-7,13-14H2,1-3H3/t15-,17-/m0/s1

InChIKey = BRRGNOFUBFINSX-RDJZCZTQSA-N

(3; R = CH2CHCH2) [150296-38-1] C15H21NO (MW 231.37)

InChI = 1S/C15H21NO/c1-4-11-16(12-5-2)13(3)15(17)14-9-7-6-8-10-14/h4-10,13,15,17H,1-2,11-12H2,3H3/t13-,15-/m0/s1

InChIKey = JIIURWPYHCVOGX-ZFWWWQNUSA-N

(4; R = Ph(CH2)4) [132284-82-3] C29H37NO (MW 415.67)

InChI = 1S/C29H37NO/c1-25(29(31)28-21-9-4-10-22-28)30(23-13-11-19-26-15-5-2-6-16-26)24-14-12-20-27-17-7-3-8-18-27/h2-10,15-18,21-22,25,29,31H,11-14,19-20,23-24H2,1H3/t25-,29-/m0/s1

InChIKey = RKJMHOOVDGYHBZ-SVEHJYQDSA-N

(5; R = (CH2)5) [133576-76-8] C14H21NO (MW 219.36)





InChI = 1S/C14H21NO/c1-12(15-10-6-3-7-11-15)14(16)13-8-4-2-5-9-13/h2,4-5,8-9,12,14,16H,3,6-7,10-11H2,1H3/t12-,14-/m0/s1



InChIKey = CYPOTTRENVPAPL-JSGCOSHPSA-N



(chiral ligand for the enantioselective reduction of ketones with lithium aluminum hydride; chiral auxiliary for the diastereoselective aldol condensation; chiral catalyst for the enantioselective Darzens reaction; chiral catalyst for the enantioselective alkylation of aldehydes with dialkylzincs; chiral catalyst for the enantioselective conjugate addition of dialkylzincs to enones; chiral catalyst for the enantioselective alkylation of imines with dialkylzincs; chiral catalyst for the enantioselective Michael addition of nitromethane to α,β-unsaturated ketones)



Alternate Name: [R-(R,S)]-α-[1-(dimethylamino)ethyl]benzenemethanol.



Physical Data: (1) mp 86–88 °C; [α]D21 −29.2° (c 5, MeOH). (2) bp 170 °C/2 mmHg; [α]D25 + 24.4° (c 2, hexane).



Solubility: sol many organic solvents.



Form Supplied in: (1) colorless crystals; (2) colorless oil; (1) and (2) are commercially available.

(1R,2S)‐N‐Methylephedrine

Pyrimidyl alkanol was found to act as an asymmetric autocatalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde. Asymmetric autocatalysis of 2-alkynylpyrimidyl alkanol with an extremely low enantiomeric excess (ca. 0.00005% ee) exhibits enormous asymmetric amplification to afford the same compound with >99.5% ee. This asymmetric autocatalysis with amplification of ee has been employed to examine the validity of proposed theories of the origins of homochirality. Circularly polarized light, quartz, sodium chlorate, cinnabar, chiral organic crystals and spontaneous absolute asymmetric synthesis were considered as possible candidates for the origin of chirality; each could act as a chiral source in asymmetric autocatalysis. Asymmetric autocatalysis can discriminate the isotope chirality arising from the small difference between carbon (carbon-13/carbon-12) and hydrogen (D/H) isotopes. Cryptochiral compounds were also discriminated by asymmetric autocatalysis.

Kenso Soai

Papers

Enantioselective Reformatsky Reaction with Ketones. Asymmetric Synthesis of β‐(tert‐Hydroxy) Esters.

Asymmetric Synthesis with a Chiral Catalyst Generated from Asymmetric Autocatalysis.

Asymmetric Synthesis of 3-Quinolylalkylamine by Enantioselective Alkylation of N-Diphenylphosphinyl-3-quinolylimine Using Chiral β-Amino Alcohols.

(1R,2S)‐N‐Methylephedrine

The Origins of Homochirality Examined by Using Asymmetric Autocatalysis