138374-16-0

Upstream product

• 15356-60-2 (1S,2R,5S)-(+)-menthol 

Downstream Products

• 95456-30-7 syn-9-(Menthyloxy)-9-phosphabicyclo<4.2.1>nona-2,4,7-trien 

Relevant academic research and scientific papers

Rh-catalyzed enantioselective conjugate addition of arylboronic acids with a dynamic library of chiral tropos phosphorus ligands

A library of 19 chiral tropos phosphorus ligands, based on a free-to-rotate (tropos) biphenol unit and a chiral P-bonded alcohol (11 phosphites, 1-P(O)2O to 11-P(O)2O) or secondary amine (8 phosphoramidites, 12-P(O)2N to 19-P(O)2N). were screened, individually and in combinations of two, in the rhodium-catalyzed asymmetric conjugate addition of arylboronic acids to enones and enoates. High enantioselectivities (up to 99% ee) and excellent yields were obtained in the addition to either cyclic or acyclic substrates. The flexible biphenolic P ligands outperformed the analogous rigid binaphtholic P ligands. Variable-temperature 31P NMR studies revealed that the biphenolic ligands are tropos even at low temperature. Only below 190 K was a coalescence observed: upon further cooling, two atropisomers were detected. The Rh homocomplexes ([Rh(La)2]+) were also studied: in general, a single doublet (P-Rh coupling) was observed in the case of the biphenolic phosphite ligands, over the temperature range 380-230 K, demonstrating their tropos nature in the rhodium complexes even at low temperatures. On the other hand, the phosphoramidites showed different behaviors depending on the structure of the ligand and on the nature of the rhodium source. The spectrum at 230 K of the mixture of [Rh(acac)(eth)2] (eth = C2H4) with phosphite 6-P(O)2O and phosphoramidite 19-P(O)2N (the most enantioselective ligand combination in the conjugate addition reaction) revealed the presence of four homocomplexes (total approximately 40%: [Rh(6-P(O)2}2], [Rh{(aR)-19-P(O)2N}2], [Rh((aS)-19-P(O)2N) 2], [Rh((aR)-19-P(O)2N}((aS)-19-P(O)2N}]) and one heterocomplex, [Rh{6-P(O)2O){(aR)-19-P(O)2NJ] (approximately 60%) In the heterocomplex, the biphenol-derived phosphite is free to rotate (tropos) while the biphenol-derived phosphoramidite shows a temperature-dependent tropos/atropos behavior (coalescence temperature = 310 K).

Rh-catalyzed asymmetric hydrogenation of prochiral olefins with a dynamic library of chiral TROPOS phosphorus ligands

A library of 19 chiral tropos phosphorus ligands, based on a flexible (tropos) biphenol unit and a chiral P-bound alcohol (11 phosphites) or secondary amine (8 phosphoramidites), was synthesized. These ligands were screened, individually and as a combination of two, in the rhodium-catalyzed asymmetric hydrogenation of dehydro-α-amino acids, dehydro-β-amino acids, enamides and dimethyl itaconate. ee values up to 98% were obtained for the dehydro-α-amino acids, by using the best combination of ligands, a phosphite [4-P(O)2O] and a phosphora midite [13-P(O)2N]. Kinetic studies of the reactions with the single ligands and with the combination of phosphite [4-P(O)2O] and phosphoramidite [13-P(O) 2N] have shown that the phosphite, despite being less enantioselective, promotes the hydrogenation of methyl 2-acetamidoacrylate and methyl 2-acetamidocinnamate faster than the mixture of the same phosphite with the phosphoramidite, while the phosphoramidite alone is much less active. In this way, the reaction was optimized by lowering the phosphite/phosphoramidite ratio (the best ratio is 0.25 equiv phosphite/1.75 equiv phosphoramidite) with a resulting improvement of the product enantiomeric excess. A simple mathematical model for a better understanding of the variation of the enantiomeric excess with the phosphite/ phosphoramidite ratio is also presented.

Enantioselective conjugate addition of phenylboronic acid to enones catalysed by a chiral tropos/atropos rhodium complex at the coalescence temperature

A highly enantioselective rhodium-catalysed conjugate addition of phenylboronic acid to cyclic enones has been achieved using a dynamic library of chiral phosphorus ligands; the tropos/atropos nature of the ligands in the rhodium complex has been characterised via 31P-NMR. The Royal Society of Chemistry 2005.

Enantioselective hydrogenation of itaconate using rhodium bihelicenol phosphite complex. Matched/mismatched phenomena between helical and axial chirality

Phosphites prepared from bihelicenol, menthol (or 1-phenylethanol), and PCl3 are effective ligands for the rhodium-catalyzed enantioselective hydrogenation of dimethyl itaconate. Stereochemistry of the helicene moiety plays an important role in

Molecular recognition of pyranosides by a family of trimeric, 1,1'- binaphthalene-derived cyclophane receptors

The synthesis and carbohydrate-recognition properties of a new family of optically active cyclophane receptors, 1-3, in which three 1,1'- binaphthalene-2,2'-diol spacers are interconnected by three buta-1,3- diynediyl linkers, are described. The macrocycles all contain highly preorganized cavities lined with six convergent OH groups for H-bonding and complementary in size and shape to monosaccharides. Compounds 1-3 differ by the functionality attached to the major groove of the 1,1'-binaphthalene- 2,2'-diol spacers. The major grooves of the spacers in 2 are unsubstituted, whereas those in 1 bear benzyloxy (BnO) groups in the 7,7'-positions and those in 3 2-phenylethyl groups in the 6,6'-positions. The preparation of the more planar, D3-symmetrical receptors (R,R,R)-1 (Schemes 1 and 2), (S,S,S)- 1 (Scheme 4), (S,S,S)-2 (Scheme 5), and (S,S,S)-3 (Scheme 8) involved as key step the Glaser-Hay cyclotrimerization of the corresponding OH-protected 3,3'-diethynyl-1-1'-binaphthalene-2,2'-diol precursors, which yielded tetrameric and pentameric macrocycles in addition to the desired trimeric compounds. The synthesis of the less planar, C2-symmetrical receptors (R,R,S)-2 (Scheme 6) and (S,S,R)-3 (Scheme 9) proceeded via two Glaser-Hay coupling steps. First, two monomeric precursors of identical configuration were oxidatively coupled to give a dimeric intermediate which was then subjected to macrocyclization with a third monomeric 1,1'-binaphthalene precursor of opposite configuration. The 3,3'-dialkynylation of the OH- protected 1,1'-binaphthalene-2,2'-diol precursors for the macrocyclizations was either performed by Stille (Scheme 1) or by Sonogashira (Schemes 4, 5, and 8) cross-coupling reactions. The flat D3-symmetrical receptors (R,R,R)- 1 and (S,S,S)-1 formed 1:1 cavity inclusion complexes with octyl 1-O- pyranosides in CDCl3 (300 K) with moderate stability (ΔG0 ca. -3 kcal mol-1) as well as moderate diastereo(Δ(ΔG0) up to 0.7 kcal mol-1) and enantioselectivity (Δ(ΔG0) =0.4 kcal mol-1) (Table 1). Stoichiometric 1:1 complexation by (S,S,S)-2 and (S,S,S)-3 could not be investigated by 1H- NMR binding titrations, due to very strong signal broadening. This broadening of the 1H-NMR resonances is presumably indicative of higher-order associations, in which the planar macrocycles sandwich the carbohydrate guests. The less planar C2-symmetrical receptor (S,S,R)-3 formed stable 1:1 complexes with binding free enthalpies of up to ΔG0 = - 5.0 kcal mol-1 (Table 2). With diastereoselectivities up to Δ(ΔG0) = 1.3 kcal mol-1 and enantioselectivities of Δ(ΔG0)= 0.9 kcal mol-1, (S,S,R)-3 is among the most selective artificial carbohydrate receptors known.