Heliotropine from Safrole

To prepare heliotropin from isosafrol (which results from the isomerisation of safrol with alkalis), 5 parts of isosafrol are treated with a solution of 25 parts of potassium bichromate, 38 parts of cioncentrated sulphuric acid, and 80 parts of water. The reaction product is steam distilled and the distillate is extracted with ether, and the heliotropin obtained is purihed by means of alkaline bisulphite in the usual manner. 

Heliotropin is prepared commercially by the synthesis given above from safrole through iso-safrole. It is used in perfumes on account of its very pleasant odor of heliotrope flowers. It forms crystals, m.p. 37°, b.p. 263°. By boiling with water it hydrolyzes and yields protocatechuic aldehyde just as vanillin does. It also yields oximes and hydrazones which are characteristic. 

This relationship explains the similarity of the names and the fact that both are obtained from gum catechin. The reverse of the above reaction, the synthesis of protocatechuic acid from pyrocatechinol, may be accomplished by heating the phenol with ammonium carbonate and water to 1400° under pressure, which is a modification of the Kolbe reaction for synthesizing salicyclic acid (p. 716). From its constitution and by reference to the formulas on page 662 we will see its relationship to vanillin, heliotropin, eugenole, safrole, guaiacol, etc. 

In general heliotropin is manufactured from safrole, which is a component of many... 

Isosafrol results from the isomerisation of safrol by heating with alcoholic potash, and this conversion is the preliminary step in the manufacture of heliotropine since isosafrol yields considerably more heliotropine on oxidation than safrol does. Isosafrol has the following constitution —... 

Sassafras oil is used as a generic term for commercial essential oils containing high quantities of safrole. They originate from different botanical species. The main use of these oils is the isolation of safrole as the starting material for the production of heliotropin (see p. 136)... 

The conversion of eugenole into iso-eugenole and of safrole into iso-safrole is accomplished by boiling with alcoholic potassium hydroxide. The oxidation products of these ethers are other important essential oil constituents. Eugenole yields the corresponing aldehyde which is known as vanillin, the chief constituent of vanilla beans from which vanilla extract is made. Safrole by oxidation yields a compound known as piperonal also as heliotropine. It has the odor of heliotrope flowers and is used as artificial heliotrope essence. These latter compounds and also constituents of other essential oils will be considered in detail later in their proper chemical relationship (p. 66i, etc.). 

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