Reaktion #490359

Reaktionsgleichung

CHCl3

hydrogen

3-(tert-Butyl-dimethyl-silanyloxymethyl)-5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid benzyl ester

hydrogen

→

3-(tert-butyl-dimethyl-silanyloxymethyl)-5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid

Ausbeute 85.1%

Lösungsmittel

CH2Cl2

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONwere added
2. 2
   Filtrationthe Pd/C was filtered off
3. 3
   workup.ADDITIONafter adding MgSO4 as an aid
4. 4
   Temperaturto increase particle size
5. 5
   WaschenThe CH2Cl2-CHCl3 phase was washed with 200 mL of 0.1N HCl
6. 6
   Sonstigeto remove the by-product benzyl alcohol
7. 7
   SonstigeThe organic layer was dried
8. 8
   Sonstigeevaporated

Vorschrift

9.63 g of 3-(tert-Butyl-dimethyl-silanyloxymethyl)-5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid benzyl ester was dissolved in ca. 125 mL of dry CH2Cl2. The solution was transferred to a Parr hydrogenation bottle, and 5 g of 5% Pd on carbon were added. The bottle was charged with hydrogen and shaken on a Pair hydrogenation apparatus for 3 hours; hydrogen uptake ceased after 2 hours, as indicated by pressure monitoring. 100 mL CHCl3 were added, and the Pd/C was filtered off after adding MgSO4 as an aid to increase particle size. The CH2Cl2-CHCl3 phase was washed with 200 mL of 0.1N HCl to remove the by-product benzyl alcohol. The organic layer was dried and evaporated to give 6.47 g 3-(tert-butyl-dimethyl-silanyloxymethyl)-5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid, after trace solvent removal in a vacuum oven. TLC Rf=0.55 (1:1 ethyl acetate:hexane). Note: (a) Pd catalyzed hydrogenation is a far superior method to triethylsilane/palladium diacetate for this benzyl ester cleavage, (b) washing product with weak aqueous acid is a good way to remove benzyl alcohol. 1H NMR (300 MHz, CDCl3) δ (ppm): 7.55 (d, 1H), 6.7 (d, 1H), 4.3 (d, 1H), 4.17 (m, 1H), 4.02 (dd, 1H), 3.82 (dd, 1H), 3.75 (dd, 1H), (2.45 (s, 3H), 0.8 (s, 9H), 0.01 (s, 3H).

Quelle