《Alternatives to Phosphinooxazoline (t-BuPHOX) Ligands in the Metal-Catalyzed Hydrogenation of Minimally Functionalized Olefins and Cyclic β-Enamides》 was published in Advanced Synthesis & Catalysis in 2017. These research results belong to Biosca, Maria; Magre, Marc; Coll, Merce; Pamies, Oscar; Dieguez, Montserrat. Synthetic Route of C24H34O2 The article mentions the following:
A new series of readily accessible iridium- and rhodium-phosphite/oxazoline catalytic systems that can efficiently hydrogenate, for the first time, both minimally functionalized olefins and functionalized olefins, such as Et 3-phenylbut-2-enoate, Et (2Z)-3-cyclohexyl-3-phenylprop-2-enoate, [(1E)-1-methyl-1-propen-1-yl]benzene, etc. (62 examples in total), with high enantioselectivities (up to >99% ee) and conversions has been reported. The phosphite-oxazoline ligands, which are readily available in only two synthetic steps, are derived from previous privileged 4-alkyl-2-[2-(diphenylphosphino)phenyl]-2-oxazoline (PHOX) ligands by replacing the phosphine moiety by a biaryl phosphite group and/or the introduction of a methylene spacer between the oxazoline and the Ph ring. The modular design of the ligands has given the opportunity not only to overcome the limitations of the iridium-PHOX catalytic systems in the hydrogenation of minimally functionalized Z-olefins and 1,1-disubstituted olefins, but also to expand their use to unfunctionalized olefins containing other challenging scaffolds (e.g., exocyclic benzo-fused and triaryl-substituted olefins) and also to olefins with poorly coordinative groups (e.g., α,β-unsaturated lactams, lactones, alkenylboronic esters, etc.) with enantioselectivities typically >95% ee. Moreover, both enantiomers of the hydrogenation product could be obtained by simply changing the configuration of the biaryl phosphite moiety. Remarkably, the new catalytic systems also provided excellent enantioselectivities (up to 99% ee) in the asym. hydrogenation of another challenging class of olefins – the functionalized cyclic β-enamides, such as N-(6-bromo-3,4-dihydronaphthalen-2-yl)acetamide, N-(2H-chromen-3-yl)acetamide, N-(8-methoxy-3,4-dihydronaphthalen-2-yl)acetamide, etc. Again, both enantiomers of the reduced amides could be obtained by changing the metal from Ir to Rh. The environmentally friendly propylene carbonate which can be used with no loss of enantioselectivity was also demonstrated. Another advantage of the new ligands over the PHOX ligands is that the best ligands are derived from the affordable (S)-phenylglycinol rather than from the expensive (S)-tert-leucinol.(R)-3,3′-Di-tert-butyl-5,5′,6,6′-tetramethylbiphenyl-2,2′-diol(cas: 329735-68-4Synthetic Route of C24H34O2) was used in this study.
(R)-3,3′-Di-tert-butyl-5,5′,6,6′-tetramethylbiphenyl-2,2′-diol(cas: 329735-68-4) belongs to phenols. Phenols are more acidic than typical alcohols. The acidity of the hydroxyl group in phenols is commonly intermediate between that of aliphatic alcohols and carboxylic acids (their pKa is usually between 10 and 12).Synthetic Route of C24H34O2
Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts