Manufacture of oct-3,5-dien-2,7-dione and oct-4-en-2,7-dione from oct-7-ol-3,5-dien-1-yne

摘要

Oct-3,5-dien-2,7-dione is prepared by oxidising oct-7-ol-3,5-dien-1-yne to oct-7-one-3,5-dien-1-yne and hydrating the latter to form the desired dienic dione or by hydrating the oct-7-ol-3,5-diene-1-yne to oct-7-ol-3,5-dien-2-one and oxidising the latter to the dienic dione. Both oxidations of the CH.OH group to a carbonyl group may be effected with a slurry of manganese dioxide in an inert organic solvent; with tertiary butyl chromate; or with an aluminium tertiary alkoxide in the presence of a hydrogen acceptor. The hydrations of the acetylenic bond to form a carbonyl group may be effected in an aqueous methanol or acetone or other aqueous solvent system which may contain a hydration catalyst such as sulphuric, phosphoric or formic acid in combination with a mercury compound such as mercuric oxide or p sulphate, or which may contain perchloric acid or BF3, alone or with a mercury compound. The resulting oct-dienic dione may be converted into oct-4-en-2,7-dione by partial hydrogenation by treatment, for example, with a metal-acid combination such as zinc and acetic acid, in an amine solvent such as pyridine. The oct-7-ol-3,5-dien-1-yne starting material may be prepared by ethylynating sorbaldehyde and subjecting the resulting oct-4,6-dien-3-ol-1-yne to an alkylic rearrangement. The ethylynation may be effected by reacting the sorbaldehyde with a Grignard reactant CH­C.MgX or with the acetylide of a basic metal such as lithium, sodium, potassium or calcium, if desired in a solvent, and hydrolysing the resulting complex, e.g. with aqueous brine or NH4Cl solution. The basic metal acetylide may be preformed or may be formed in situ by using liquid ammonia as a solvent and adding the metal and then acetylene thereto. The alkylic rearrangement may be effected by treating with an aqueous solution of sulphuric, hydrochloric, phosphoric, formic, acetic, trichloracetic or other acid, preferably in the presence of an anti-oxidant such as hydroquinone, butylated hydroxy anisole or butylated hydroxytoluene, under an inert atmosphere. Examples describe the synthesis of oct-4-en-2,7-dione from sorbaldehyde by both multi-stage processes described above, the intermediates being isolated and purified after each stage.