CS196005B1 - Process for preparing 2-phenylethanole - Google Patents

Description

The invention relates to a process for the preparation of 2-phenylethanol

2-Phenylethanol is one of the most important components of perfume compositions and is also an intermediate product. for the synthesis of other fragrances, esters, phenylacetaldehyde and its acetals and the like. Several processes for the production of 2-phenylethanol are known, the most practical being of hydrogenolysis of atyrene oxide and the Friedel-Crafts reaction of benzene with ethylene oxide.

Other procedures are based on less accessible raw materials and are of a laboratory nature. These include, for example, the reduction of phenylacetic acid and its functional derivatives, the cleavage of benzyl ethers, the preparation of styrene and trialkylboranes and alkylaluminium halides, the preparation of phenylorgank, benzyl alcohol, alphachlortoluene and the like. Among the economically attractive processes is the recently described method according to German Patent Specification No. 2219953, consisting in hydrogenolysis of 1-phenyl-1,2-ethanediol on a palladium catalyst. The reaction is highly selective and can be carried out in both liquid and gaseous phases, as described in L. Cerveny, A. Marhoula, Z. Berka and V. Ruzicka in Chem.prum. (in print) · The most preferred method of preparing 1-phenyl-1,2-ethanediple is probably the oxidation of styrene with hydrogen peroxide in formic cyeeline, as described in Naveae Y.R. in Helv. Chim.Acta 22, 319 (1967) and Gunston F.D. in Advan. Org. Chem. 1, 163 (1966). The reaction produces two semi-esters of 1-phenyl-1,2-ethanediol β formic acid, which, after distilling off the excess formic acid, alkalinizes. The resulting 1-phenyl-1,2-ethanediol can then be converted by hydrogenolysis to 3-phenyl196,005

19B OOS .2 ethanol.

The disadvantage of this process is the necessity of saponification of 1-phenyl-1,2-ethanediol semi-esters with formic acid, does not entail considerable consumption of alkaline hydroxide, necessity of neutralization of the reaction mixture after the hydrolysis and separation of 1-phenyl-, 1,2-ethanediol from the reaction mixtures, most often by extraction, drying of the extract and distillation. Considerable labor and chemical consumption make this process of 2-phenylethanol more expensive.

These disadvantages are largely eliminated by the process of the present invention for the preparation of 2-phenyl-ethanol by subjecting 1-phanyl-1,2-ethanediol formates to catalytic hydrogenolysis in the presence of a palladium or platinum catalyst. The reaction proceeds without measurable hydrogen consumption e can be represented by the formula

Fh-CH (OH) -OCOH

Fh-CH (OCOH) -CH 8 -CH

Ph - CHg-CHg ·

The hydrogen required for hydrogenolysis monoformate formed in the reaction mixture a catalytic decomposition éřejmě formylevého residue after hydrogenolysis, for example, dropped by the following formula ⁰

-CHg-O-O-H + Hjj

- * Ca, -OH + -O- ^β-, + H ^{t +)} kΛ -A

CH, OH -

AND

H ₂ + 00 • 7 CH ₂ · 0 Hg 1 CO

Most likely, direct disintegration into hydrogen and carbon monoxide without transient formation of methanol or formaldehyde.

The reaction preferably proceeds from the presence of a water-dissolving solvent (alcohols, glycols), or water otherwise causes the catalyst to agglomerate, thereby reducing the reaction rate.

Since the only product in addition to a small amount of ethylbenzene is 2-phenylethanol, hydrogenolysis of the secondary -OH group occurs under given conditions.

The procedure is apparent from the following examples of a specific embodiment.

Example 1

A 150 ml stainless steel autoclave was charged with 30 ml of a 50% solution of 1-phenyl-1,2-ethanediol semi-formate in ethanol and 1 g of 3% Bd on activated carbon catalyst. 10.9 MPa (111 kp / cm ² ). Hydrogenolysis was carried out without measurable hydrogen consumption. After 150 minutes, the reaction roots contained 95 wt. % Of 2-phenylethanol and 5 wt. ethylbenzene (not considered ethanol) in total conversion of half-oxenates.

Example 2

Hydrogenolysis of 1-phenyl-1,2-ethanediol semi-formates was carried out analogously to that

198 005 in Example 1 at a temperature of 150 ° C and a pressure of 117.6 kPa (1.2 kp / cm 2). 1-Butanol was used as solvent, 1 g of 5% Pt on activated carbon was used as catalyst. The yield of 2-phenylethanol was. same as Example 1.

Claims (1)

A process for the preparation of 2-phenylethanol, characterized in that the 1-phenyl-1,2-ethanediol half-formates are subjected to catalytic hydrogenolysis in the presence of a palladium or platinum catalyst.