Phenylpropargyl aldehydes

PHENYLPROPARGYL ALDEHYDE DIETHYL ACETAL (Propiolaldehyde, phenyl-, diethyl acetal)... 

C. Phenylpropargyl aldehyde acetal. A solution of 20.7 g. (0.25 mole) of potassium hydroxide in 200 ml. of absolute ethanol is added to SO g. (0.18 mole) of o-bromocinnamic aldehyde acetal in a 500-ml. flask. The mixture is refluxed for 1.5 hours and poured into a 3-1. separatory funnel containing 1.5 1. of water. The oil which separates is extracted with three 170-ml. portions of chloroform, and the combined chloroform extracts are washed with three 75-ml. portions of water and then dried over 15 g. of anhydrous sodium sulfate. The chloroform is removed by distillation, and the residual oil is distilled from a modified Claisen flask. The yield of phenylpropargyl aldehyde acetal boiling at 153-156°/19 mm. is 28-31 g. (80-86%). 

D. Phenylpropargyl aldehyde. Twenty-nine grams (0.14 mole) of the acetal is added to 140 ml. of water containing 10 ml. of concentrated sulfuric acid, and the mixture is heated on a steam bath with occasional shaking for 30 minutes. The aldehyde is then steam-distilled and extracted from the distillate with two 250-ml. portions of ether. The ethereal solution is dried over 20 g. of anhydrous sodium sulfate, the solvent is removed, and the residue is distilled from a 100-ml. modified Claisen flask. The yield of phenylpropargyl aldehyde boiling at 114—117°/17 mm. and with 1.6032 is 13-15 g. (70-81%). 

The procedure given for the preparation of phenylpropargyl aldehyde is a modification of Claisen s directions3 in part due to Kalff.4 The monobromocinnamic aldehyde was described by Zincke.5 Other methods of possible preparative value for the acetal are the interaction of sodium phenylacetylene,6 9 or the Grignard reagent from phenylacetylene,10 11 and ethyl ortho-formate. 

Phenylpropargyl aldehyde and 4-methoxyaniline were refluxed in a benzene solution in the presence of a catalytic amount of p-toluenesulfonic acid under Dean-Stark conditions. After cooling the mixture was filtered through silica gel to remove residual amine. The imine purity was checked by H-NMR and the product isolated. 

A synthesis of phenylpropargyl aldehyde less efficient than that described above is of interest in demonstrating acetal formation as a means of protecting an aldehyde function during dehydrohalogenation with a strong base. ... 

Phenyl-2-propanone, 669 Phenylpropargyl alcohol, 593 Phenylpropargyl aldehyde, 1205, 1206... 

A route to a, 8-acetylenic aldehydes is based on the fact that triethyl orthoformate in the presence of zinc iodide as catalyst reacts with a terminal acetylene with elimination of ethanol and formation of an acetal, as illustrated for the preparation of phenylpropargyl aldehyde. The reactants are heated neat with the catalyst to about 135°, and ethanol is removed by distillation (about 1 hr.). 

Phenyl neopentyl sulfide, 272 Phenyl oxime-O-sulfonates, 456 2-Phenyloxirane, 219 Phenylpropargyl aldehydes, 6 Phenylselenenyl bromide, 459-460 Phenylselenenyl chloride, 459-460 Phenylselenenyi trifluoroacetate, 459 Phenylselenlnyl chloride, 459-460 ot-Phenylseleno ketones, 459 Phenylselenol, 235, 362 Phenylsulfinylcarbene, 457... 

Prenylnaphthalene, 24, 84 Pbenylpropargyl aldehyde, 25,92 Phenylpropargyl aldehyde acetal, 25,93... 

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