Yield:52010-97-6 83% ，589-29-7 17%

Reaction Conditions:

with C₄₈H₄₃ClN₂P₂Ru;ammonium formate in water;toluene at 90; for 9 h;Catalytic behavior;Schlenk technique;

Steps:

31 Example 31
Transfer hydrogenation in a biphasic system with formate salts as hydride donor on aldehyde substrates The selected aldehyde (2.5 mmol), HCOONH₄ (10 mmol, 0.63 g) and complex (e.g. 1 .25 μηιοΙ, 1 mg; S/C = 2000) are transferred into a 50 ml Schlenk tube. Then toluene (1 .2 ml) and water (5 ml) are sequentially added. The biphasic mixture is subjected to four vacuum-argon cycles under vigorous stirring and then put into an oil bath at 90°C for the desired time. The reaction is sampled by removing ~1 ml of the mixture, diethyl ether (4 ml) is added, the organic phase separated, dried over MgS0₄, filtered and the solvent gently removed under reduced pressure. The crude residue was dissolved with CDCI₃ and analyzed by H-NMR. Alternatively, the dried organic fraction is filtered over a short silica pad and the conversion determined by GC analysis. Table 11. TH of aldehydes catalyzed by complexes 13-15 with HC0₂NH₄ in toluene/H₂0 at 90°C Aldehyde Complex S/C Substrate NH₄-formate Time Alcohol By- molar molar;equivalents (h) (%) products (%L_ 13 5000 0.5 1 ; 2 16 60 0 13 5000 0.5 1 ; 2 22 76 0 14 5000 0.5 1 ; 2 15 96 0 14 5000 0.5 1 ; 2 24 97 0 14 5000 1 .0 1 ; 2 15 86 0 14 5000 1.0 1; 2 24 95 0 14 5000 0.5 1; 4 15 96 0 14 5000 0.5 1; 4 24 96 0 14 5000 1.0 1; 4 15 96 0 14 5000 1.0 1; 4 24 96 0 14 20000 2.0 2; 4 24 94 0 14 20000 2.0 2; 4 48 96 0 15 5000 0.5 1; 2 16 96 0 15 10000 2.0 1; 2 20 86 0 15 20000 2.0 1; 2 40 96 0 14 2000 0.5 1; 2 10 97 0 14 20000 2.0 2; 4 24 62 0 14 20000 2.0 2; 4 48 72 0 14 2000 0.5 2; 4 10 >99 0 14 2000 0.5 1; 2 3.5 >99 0 14 2000 0.5 1; 1.5 9 57: 83 0 58: 17 14 2000 0.5 1; 2 10 57: 71 0 58: 21 0 14 2000 0.5 1;4 10 57: 0 58: 99 14 2000 0.5 1; 2 10 97 54:10 14 5000 2.0 2; 4 16 78 0 14 5000 2.0 2; 4 24 86 0 14 5000 2.0 2; 4 48 97 0 14 5000 2.0 4; 4 16 84 0 14 5000 2.0 4; 4 24 91 0 14 5000 2.0 4; 4 48 94 0 14 10000 0.5 1;2 24 38 0 14 10000 0.5 1;2 38 49 0 With complexes 13-15 the transfer hydrogenation of aldehydes with NH₄-formate is an improvement compared to using 2-propanol as hydride donor and K₂C0₃ as base (examples 28 and 29). The use of less complex (higher S/C ratio) is possible and less by-products are formed. It is important to note that no primary amines are produced by reductive amination of the aldehyde. Interestingly, the presence of the toluene solvent as co-solvent is not entirely required, as shown in the table below. Toluene was not added to the reactions carried out on a 2.5 mmol substrate scale. Table 12. TH of aldehydes catalyzed by complex 14 with HC0₂NH₄in H₂0 at 90°C Aldehyde Complex S/C Substrate NH₄-formate Time Alcohol By- molar molar;equivalents (h) (%) products (%) 13 5000 0.5 1; 2 16 60 13 5000 0.5 1; 2 22 76 14 2000 2.5 mmol 1; 2 2 50 14 2000 2.5 mmol 1; 2 4 76 14 2000 2.5 mmol 1; 2 7 97 14 5000 2.5 mmol 1; 2 14 53 14 5000 2.5 mmol 1; 4 24 97 14 5000 2.5 mmol 2; 4 24 90 45 14 5000 0.5 1; 2 15 96 14 5000 0.5 1; 2 24 97 14 5000 1.0 1; 2 15 86 14 5000 1.0 1; 2 24 95 14 5000 0.5 1; 4 15 96 14 5000 0.5 1; 4 24 96 14 5000 1.0 1; 4 15 96 14 5000 1.0 1; 4 24 96 14 20000 2.0 2; 4 24 94 14 20000 2.0 2; 4 48 96 0 15 5000 0.5 1; 2 16 96 0 15 10000 2.0 1; 2 20 86 0 15 20000 2.0 1; 2 40 96 0 14 2000 2.5 mmol 1; 2 14 33 6 14 2000 2.5 mmol 1; 2 16 61 0 14 2000 0.5 1; 2 10 97 0 46 14 2000 2.0 2;4 11 97 0 14 10000 2.0 2;4 24 24 0 14 20000 2.0 2; 4 24 62 0 14 20000 2.0 2; 4 48 72 0 14 5000 2.0 2; 4 15 96 0 47 >99, 14 2000 0.5 2; 4 10 0 48 65^[bl 14 2000 0.5 1; 2 3.5 >99 0 55 14 2000 2.0 2;4 3.5 99, 65^[bl 0 14 2000 0.5 1; 1.5 9 57: 83 0 56 58: 17 14 2000 0.5 1; 2 10 57: 71 0 58: 21 14 2000 0.5 1;4 10 57: 0 0 58: 99 14 2000 0.5 1; 2 10 97 54:10 14 5000 2.0 2; 4 16 78 54:6 14 5000 2.0 2; 4 24 86 0 52 14 5000 2.0 2; 4 48 97 54:12 14 5000 2.0 4; 4 16 84 0 14 5000 2.0 4; 4 24 92 54:5 14 5000 2.0 4; 4 48 94 54:7 14 10000 0.5 1 ; 2 24 38 14 10000 0.5 1 ; 2 38 49 59 14 10000 2.0 4; 4 20 98 0 60 14 10000 2.0 2; 4 24 65 0 60 14 10000 2.0 4; 4 24 97 0 61 14 5000 2.0 4;4 20 98, 88^[bl 62 14 5000 2.0 2;4 8 95 63 14 2000 2.0 4;4 9 96, 79^[bl Conversion and product content were determined by GC analysis or by -NMR spectroscopy. Isolated yield. On 2.5 mmol scale, reduction of benzaldehyde 45 (0.5 molar in toluene) at S/C =2000, 90°C and 4 equivalents of 2M aqueous Na-formate gave only traces of benzylalcohol after 14 hours. Use of 4 equivalents of (NEt₃H)-formate improves the yield to 50 % in 22 hours. Use of 5 equivalents of (NEt₃H)-formate on frans-cinnamaldehyde 52 gives after 18 hours 80 % of allylic alcohol 53 and 15 % of saturated alcohol 54. NH₄-formate is preferred over the other formate reagents.

References:

JOHNSON MATTHEY PUBLIC LIMITED COMPANY;BALDINO, Salvatore;BARATTA, Walter;BLACKABY, Andrew;BRYAN, Richard, Charles;FACCHETTI, Sarah;JURCIK, Vaclav;NEDDEN, Hans, Guenter WO2016/193761, 2016, A1 Location in patent:Page/Page column 85-87