Process for preparing isochroman compounds

Details Process for preparing isochroman compounds Process for preparing isochroman compounds

1997-11-10

1999-06-15

Raymond, Richard L.

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

549385, 549389, 549398, 549408, 549409, C07D31176, C07D31178, C07D31192

Patent

active

059123621

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a process for preparing isochroman compounds using an aqueous solution of formaldehyde having a specific concentration as a formaldehyde source. The process of the present invention is simplified and economical.
2. Description of Related Art
It has been known to date that isochroman compounds represented by the following general formula (I) have an excellent musky odor: ##STR2## wherein R.sub.1 and R.sub.2 each stands for a hydrogen atom, a lower alkyl group or a lower alkoxyl group, or alternatively R.sub.1 and R.sub.2 are respectively bonded to adjacent carbon atoms with mutual bonding of R.sub.1 and R.sub.2 together with the carbon atoms respectively bonded to R.sub.1 and R.sub.2 to form a benzene ring, a naphthalene ring, or a C.sub.5 or C.sub.6 cycloalkane or cycloalkene which may have 1 to 6 lower alkyl groups; and R.sub.3 stands for a hydrogen atom or a lower alkyl group.
Examples of the processes for preparing such isochroman compounds include: of an arylalkanol and paraformaldehyde; alkylene oxide in the presence of aluminum chloride to form a complex of an arylalkanol with aluminum chloride, partially deactivating the aluminum chloride in the complex with a substance containing a free hydroxyl group, and adding paraformaldehyde to the resulting reaction mixture to cyclize the arylalkanol; presence of a protonic acid; comprising effecting the reaction in the presence of an azeotropic agent such as n-hexane, cyclohexane, methylcyclohexane, benzene or toluene; phosphorus to a mixture of an arylalkanol, concentrated hydrochloric acid and a compound capable of releasing formaldehyde; and presence of a lower carboxylic acid anhydride or a methylene(lower carboxylate) having lower alkyl moieties in the acyl groups thereof and an acid catalyst at a high temperature.
Since the these process involve respective demerits, however, they are not well satisfactory as a process for preparing isochroman compounds.
More specifically, the process of the above item (1) involves disadvantages such as complicated operations, the necessity for the use of expensive and intractable hydrogen chloride gas, and the necessity for the removal of water formed in keeping with the progress of the reaction out of the reaction system because of the incapability of completing the reaction at the removal of water while lowering the yield and involving side reactions.
On the other hand, the process of the above item (2) involves disadvantages such as generation of hydrogen chloride gas in an intermediate treatment step (the step of partially deactivating aluminum chloride in the complex), the necessity for the use of a limited amount of a deactivator, a low yield resulting from incompletion of the reaction and occurrence of side reactions, and complicated operations in a post-treatment step (the step of recovering the reaction product).
Further, the process of the above item (3) involves disadvantages such as attainment of only an unsatisfactory yield despite the reaction effected at a high temperature over a long time according to this process, while the process of the above item (4) as an improvement thereof involves demerits such as a considerable cost involved in the recovery of an isochroman compound as the reaction product because of the use of an azeotropic agent.
Furthermore, the process of the above item (5) involves disadvantages such as generation of hydrogen chloride gas in the reaction system and attainment of only an unsatisfactory yield. On the other hand, the process of the above item (6) involves problems of complicated operations resulting from a high pressure of the reaction system because of the high-temperature reaction, and the necessity for the removal of the formed lower carboxylic acid out of the reaction system, as well as a demerit of attainment of only an unsatisfactory yield.
In view of the foregoing circumstances, the applicant has attempted the development of an improved process for preparing isochroman compounds. As

REFERENCES:
patent: 3360530 (1967-12-01), Heeringa et al.
patent: 3532719 (1970-10-01), Theimer

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