This reaction actually proceeds through several steps. First, the thriphenylphosphine abstracts a chlorine from the carbon tetrachloride.
Then, the thrichloromethanide abstracts the hydroxy hydrogen from the alcohol. The resulting alkoxy (or aryloxy) displaces the chloride in the PPh3Cl- anion.
The azide attacks the R group, a process driven forward by triphenylphosphine oxide's stability. By diluting the carbon tetrachloride with dimethylformamide, the chances of unwanted organochlorine formation is drastically lowered.
The alkyl azide is then attacked by a second triphenylphosphine, generating a phosphazide.The phosphazide attacks itself, creating a cyclic intermediate. This intermediate releases molecular nitrogen and forms an iminophosphorane. Upon work-up with water, the primary amine is formed.

The azide attacks the R group, a process driven forward by triphenylphosphine oxide's stability. By diluting the carbon tetrachloride with dimethylformamide, the chances of unwanted organochlorine formation is drastically lowered.
The alkyl azide is then attacked by a second triphenylphosphine, generating a phosphazide.The phosphazide attacks itself, creating a cyclic intermediate. This intermediate releases molecular nitrogen and forms an iminophosphorane. Upon work-up with water, the primary amine is formed.
