Conversion of bisnoralcohol to bisnoraldehyde

[0002] This application is a 371 of PCT/US94/12196 filed Oct. 27, 1994.

[0003] 1. Field of the Invention

[0004] The present invention is a process for the conversion of bisnoralcohol (I) to bisnoraldehyde (II) which is a known intermediate in the synthesis of progesterone.

[0005] 2. Description of the Related Art

[0006] The oxidation of bisnoralcohol (I) to bisnoraldehyde (II) is a well known process.

[0007] 4-hydroxy-TEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) is known, see Synthesis,190-202 and 401-414 (1971).

[0008] J. Org. Chem.,52, 2559 (1987) discloses TEMPO and 4-Methoxy-TEMPO catalyzed, two-phase oxidation of primary alcohols and secondary alcohols to aldehydes and ketones, respectively, using potassium bromide and 0.35 M sodium hypochlorite buffered to Ph 8.5 with sodium bicarbonate.

[0009] J. Org. Chem.,56, 6110 (1991) discloses the use of stoichiometric amounts of oxammonium salts, generated by treatment of TEMPO or 4-acetylamino-TEMPO with organic sulfonic acids, for the selective oxidation of primary or secondary alcohols to aldehydes or ketones, respectively.

[0010] J. Am. Chem. Soc.,106, 3374 (1984) discloses the use of TEMPO or 4-hydroxy-TEMPO to catalyze the oxidation of primary or secondary alcohols to aldehydes or ketones, respectively, by oxygen and copper (II) salts.

[0011] U.S. Pat. No. 5,136,102 discloses the use of TEMPO or 4-substituted TEMPO derivatives and a bromide containing salt to catalyze the oxidation of secondary alcohols to ketones with nitric acid and oxygen.

[0012] U.S. Pat. No. 5,155,278 discloses the use of TEMPO or 4-substituted TEMPO derivatives to catalyze the oxidation of primary alcohols to aldehydes with nitric acid and oxygen.

[0013] U.S. Pat. No. 5,155,279 discloses the use of TEMPO or 4-substituted TEMPO derivatives to catalyze the selective oxidation of primary alcohols to aldehydes with nitric acid in the absence of oxygen.

[0014] U.S. Pat. No. 5,155,280 discloses the use of TEMPO or 4-substituted TEMPO derivatives and an alkali metal nitrosodisulfonate salt to catalyze the selective oxidation of primary alcohols to aldehydes with oxygen in the absence of nitric acid.

[0015] Japanese patent J5 6152498 discloses the oxidation of bisnoralcohol to bisnoraldehyde using dimethyl sulfide and N-chlorosuccinimde or chlorine.

[0016] Disclosed is a process for the production bisnoraldehyde (II)

[0017] which comprises:

[0018] (1) forming a mixture of

[0019] (a) bisnoralcohol (I)

[0020] (b) a catalytic amount of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl in a pH range of about 8.5 to about 10.5 in a temperature range of about −10° to about 15°, and

[0021] (2) contacting the mixture of step (1) with a stoichiometric amount of hypochlorite.

[0022] Bisnoraldehyde (II) is known to be useful as an intermediate in the synthesis of progesterone and hydrocortisone, see J. Am. Chem. Soc.,74, 5933 (1952).

[0023] The present invention is practiced by (1) forming a mixture of bisnoralcohol (I), a catalytic amount of 4-hydroxy TEMPO in a pH range of about 8.5 to about 10.5 and in a temperature range of about −10° to about 15°, and (2) contacting the mixture of step (1) with a stoichiometric amount of hypochlorite. It is preferred to perform the reaction in the presence of bromide, preferably a catalytic amount of the bromide. The mixture can be cooled at any point prior to the addition of the hypochlorite.

[0024] Operable amounts of the 4-hydroxy-TEMPO are from about 0.025 mole percent to about 15 mole percent; it is preferred that the amount of the 4-hydroxy-TEMPO be from about 0.025 mole percent to about 2.5 mole percent. Operable amounts of the bromide are from about 5 mole percent to about 25 mole percent; it is preferred that the amount of bromide be from about 10 mole percent to about 15 mole percent. The pH is preferably regulated by the use of bicarbonate. Operable amounts of bicarbonate are from about 5 mole percent to about 30 mole percent; it is preferred that the amount of bicarbonate be from about 10 mole percent to about 20 mole percent. The cation of the bromide or bicarbonate is not important as long as it is soluble; preferred cation are sodium, potassium and lithium, more preferably sodium or potassium. Operable solvents include dichloroethane, toluene, ethyl acetate, methyl tert-butyl ether, dichloromethane, o-dichlorobenzene chlorobenzene and chloroform; it is preferred that the solvent be methylene chloride. While the operable solvents are organic water immiscible solvents, a small amount of water is operable and even preferred as is known to those skilled in the art. In addition, the hypochlorite is added as an aqueous mixture. It is preferred that the reaction temperature be in the range of about −5° to about 5°. It is preferred that the hypochlorite is added over a period of from about 1 hr to about 6 hr. It is preferred that the amount of hypochlorite be from about 95 mole percent to about 120 mole percent. Following step (2) it is preferred to quench the reaction mixture. Operable quenching agents include bisulfite, thiosulfate, dimethylsulfide, trimethylphosphate and triethylphosphate; it is preferred that the quenching agent be sodium or potassium thiosulfate.

[0025] The process of the present invention can be practiced in either batch mode or continuous mode as is known to those skilled in the art.

[0026] The reaction mixture is worked up by methods well known to those skilled in the art.

[0027] The bisnoraldehyde (II) can be transformed to progesterone by known methods, see J. C. S. Chem. Comm.,314 (1969) and Tet. Lett.,985 (1969).

[0028] The definitions and explanations below are for the terms as used throughout this entire document including both the specification and the claims.

[0029] All temperatures are in degrees Centigrade.

[0030] 4-hydroxy-TEMPO refers to 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl.

[0031] TEMPO refers to 2,2,6,6-tetramethylpiperidine-1-oxyl.

[0032] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, practice the present invention to its fullest extent.

[0033] The following detailed examples describe how to prepare the various compounds and/or perform the various processes of the invention and are to be construed as merely illustrative, and not limitations of the preceding disclosure in any way whatsoever. Those skilled in the art will promptly recognize appropriate variations from the procedures both as to reactants and as to reaction conditions and techniques.

[0034] A mixture of bisnoralcohol (I, 4 g), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-hydroxy-TEMPO, 10 mg), potassium bromide (133 mg), sodium bicarbonate (133 mg), dichloromethane (14 ml) and water (2.2 ml) are cooled to 1°. While maintaining this temperature, aqueous sodium hypochlorite (14%, 6.3 ml) is added over a five hr period. The reaction is complete and aqueous sodium thiosulfate is added, the two phases were separated, and the bisnoraldehyde product is crystallized by replacing the dichloromethane with heptane to give the title compound, mp=153-154°; NMR (CDCl₃) 9.56, 5.73, 2.2-2.5, 1.2-2.1, 1.20, 1.10, 0.79 δ; [α]_D²²=+83.4° (methylene chloride, c=1).

[0035] Following the general procedure of EXAMPLE 1 and making non-critical variations the process of EXAMPLE 1 is repeated at 10° and the title compound is obtained.

[0036] Following the general procedure of EXAMPLE 1 and making non-critical variations the process of EXAMPLE 1 is repeated at −10° and the title compound is obtained.

[0037] Following the general procedure of EXAMPLE 1 and making non-critical variations the process of EXAMPLE 1 is repeated using 500 mg of 4-hydroxy-TEMPO and the title compound is obtained.

[0038] Following the general procedure of EXAMPLE 1 and making non-critical variations the process of EXAMPLE 1 is repeated using 5 mg of 4-hydroxy-TEMPO and the title compound is obtained.

[0039] A mixture of bisnoralcohol (I, 6.6 g), 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl (18 mg), dichloromethane (30 ml), sodium bicarbonate (180 mg), potassium bromide (238 mg) and water (5 ml) is cooled to 1°. Then aqueous sodium hypochlorite (14.6%, 11.4 ml) is added to the mixture over a 15 min period. The reaction produced the title compound but in only a 7% conversion of bisnoralcohol with 58% selectivity for bisnoraldehyde.