New phosphine-diamine and phosphine-amino-alcohol tridentate ligands for ruthenium catalysed enantioselective hydrogenation of ketones and a concise lactone synthesis enabled by asymmetric reduction of cyano-ketones

Table 3 Enantioselective hydrogenation of ketone 13

Entry^a	Catalyst	Temp. (°C)	Conversion (%)^b	e.e. (%)^c
1	2	70	21^d	56
2	3	70	>99	49
3	8	70	37	50
4	3	50	14	54
5	4	70	<5	n.d.

^aReactions were carried out using 0.5 mol% preformed catalyst and 1 mol% KO^tBu at 70°C and 50 bar of hydrogen pressure with a 16 h reaction time unless indicated otherwise. ^bConversions were determined by ¹H NMR analysis of the crude reaction mixtures (all peaks assigned). ^cThe e.e. value was determined by chiral HPLC (Chiralpak AD-H/Chiralcel OD-H column). The absolute configuration was determined to be S by comparison of optical rotation values with literature values. ^dBase: catalyst of 50:1 used as is more common with Noyori catalysts.

ISSN: 2661-801X