DE2661074C2 - Halogenated benzyl alcohols - Google Patents

Description

The present invention relates to novel halogenated benzyl alcohols.

Some fluorinated benzyl alcohols are already known (J. Chem. Soc. C, 1967, 293; J. Chem. Soc., 1962, 3227; J. Chem. Soc., 1961, 808; J. Chem. Soc., 1959, 166; J. med. Chem., 11, 814(1968).

New halogenated benzyl alcohols of the formula

R-CH[low]2OH (I)

provided in which R has one of the following meanings:

The above-mentioned new halogenated benzyl alcohols can be prepared by known processes,

a) e.g. by reduction of the corresponding carbonyl compounds of the general formula (II)

in which R has the abovementioned meaning and Y stands for hydroxy, alkoxy, chlorine, fluorine or hydrogen, with complex metal hydrides.

Example formula scheme:

The reduction of the carbonyl function is carried out with metal hydrides such as NaBH[deep]4, LiAlH[deep]4. The reduction takes place in the presence of inert organic diluents at temperatures of 0-100°C.

When carrying out the reduction with NaBH[tief]4, suitable diluents are inert organic diluents such as ethers (e.g. diethyl ether, dioxane THF), alcohols (ethyl, methyl alcohol), their mixtures with water, and even water.

Suitable diluents for carrying out the reduction of other complex metal hydrides such as LeAlH[tief]4 are aprotic inert organic diluents such as ethers (e.g. diethyl ether, dioxane, THF).

The compounds of the general formula (II) to be reduced are dissolved in one of the diluents mentioned and the reducing agent is added. However, the compounds to be reduced can also be mixed with the reducing agent in a solvent at low temperatures (-30°C to -50°C) and the reduction can be initiated and carried out by slowly increasing the temperature (if necessary up to 50-60°C).

The reaction is usually carried out at normal pressure.

If necessary, work-up is carried out by adding to the reaction mixture an amount of water corresponding to the reducing agent used, followed by distillation of the organic phase.

When using LiAlH[tief]4, if only the carbonyl function is to be reduced, only the necessary stoichiometric amount of LiAlH[tief]4 may be used. When using weakly reducing metal hydrides as reducing agents, an excess of metal hydrides is of no importance for the course of the reaction.

Some of the carbonyl compounds required for the reduction are known. New compounds can be prepared in a known manner (see Synthesis, 1976, p. 652).

b) It is also possible to carry out the reduction of the carbonyl compound with simultaneous reductive removal of a fluorine substituent at the p-position in the nucleus.

Example formula scheme:

For this reaction, it is necessary to use LiAlH[tief]4 as a reducing agent. In addition to the amount necessary for the reduction of the carbonyl function, one reducing equivalent of LiAlH[tief]4 is required for each fluorine substituent to be removed.

Ethers, especially THF, have proven to be particularly suitable diluents.

The reduction with LiAlH[tief]4 takes place at temperatures between 20 and 100°C, preferably between 50 and 70°C. The reaction procedure and work-up are carried out as mentioned above for variant a).

The compounds of formula (I) are intermediates for the preparation of new cyclopropanecarboxylic acid esters with strong insecticidal activity, e.g. according to the following reaction schemes: where R´ is F, Cl or Br and R has the meaning given above.

Manufacturing examples

a) Reduction of polyfluorobenzoyl fluorides with preservation of nuclear substitution

0.1 mol of polyfluorobenzoyl fluoride and 0.08 mol of sodium borohydride were heated in 80 ml of absolute dioxane for 5 hours at 50°C with vigorous stirring. The mixture was then poured into water and extracted with ether to give the desired alcohols as colorless oils in 95% yield with unchanged halogen content in the aromatic core.

In this way, one can produce and spectroscopically characterize, for example:

Ir(cm[high]1): 3300, 1650, 1490, 1380, 1280, 1230, 1130, 1090, 1030, 1000, 930, 860, 750

NMR: 4.7 s (2), 2.8 s (1)

NMR (ppm) CDCl[deep]3: 4.7 s (2), 2.6 s (1)

MS m/e: 230 (M)

Reduction of polyfluorobenzoic acid fluorides with modification of the nuclear substitution

0.01 mol polyfluorobenzoyl fluoride and 0.0075 mol LiAlH[tief]4 were boiled in 80 ml abs. THF for 5 hours. After decomposition with slightly more than the calculated amount of water, the hydroxide precipitate was filtered off with suction and the benzyl alcohol defluorinated in the p-position was isolated in 80-90% yield. In this way, the following can be prepared:

Starting compound benzyl alcohol <Formula>

NMR (CDCl[deep]3), ppm:

7.2 (1), 4.6 (2),

2.9 (1)

MS

Claims (1)

1. Halogenated benzyl alcohols of the general formula R-CH[low]2OH (I) in which R for or stands.