Phenylcyclopropane from Cinnamaldehyde

The preparation of cyclopropane derivatives has been greatly facilitated by the development of carbene-type intermediates (see Chapter 13) and their ready reaction with olefins. The preparation of phenylcyclopropane from styrene and the methylene iodide-zinc reagent proceeds in only modest yield, however, and the classical preparation of cyclopropane derivatives by the decomposition of pyrazolines (first employed by Buchner in 1890) is therefore presented in the procedure as a convenient alternative. 

Caution This reaction should be carried out behind a safety screen. 

A 500-ml, three-necked, round-bottom flask is equipped with a condenser, a dropping funnel, and a thermometer in the reaction mixture. In the flask is placed a mixture of 85% hydrazine (115 ml, 118 g) and 225 ml of 95% ethanol with a few boiling chips. The solution is brought to reflux (mantle) and cinnamaldehyde (100 g, 0.76 mole) is added dropwise over about 30 minutes followed by an additional 30 minutes of refluxing. A still head is attached to the flask and volatiles (ethanol, water, hydrazine hydrate) are slowly distilled at atmospheric pressure until the pot temperature reaches 200° (about 3 hours). Hereafter, phenylcyclopropane is collected over the range 170-180°. When the pot temperature exceeds 250°, the recovery is complete. The crude product (55-65 g) is washed twice with 50-ml portions of water and dried (anhydrous potassium carbonate). Distillation under vacuum through a short column affords the product, bp 60°/13 mm, 79-80°/37 mm, n f 1.5309, about 40 g (45%). 

CARBON-CARBON BOND FORMATION BY MISCELLANEOUS REACTIONS 

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The procedure outlined is much quicker and simpler than previous methods Starting materials are readily available, and the preparation can be run on any scale in the length of a day. Because exclusion of a basic catalyst eliminates the Wolff-Kishner reduction of the cinnamalhydrazone, separation of the 5-phenylpyrazoline from cinnamalhydrazone, or of phenylcyclopropane from propenylbenzene, does not have to be effected. The present procedure can also be used to convert other ring-substituted cinnamaldehydes to the corresponding arylcyclo-propanes... 

An Organic Synthesis procedure for the 100-g scale preparation of phenylcyclopropane (2) from cinnamaldehyde (1) is available. ... 

Cyclopropanes from aj unsaturated carbonyl compounds. This new transformation is illustrated for conversion of cinnamaldehyde into phenylcyclopropane (equation I). The sequence involves Michael addition of sodium thiophenoxide... 

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