Benzenepropanol → (3-Chloropropyl)benzene

The rates of reaction of LiCl with glycol-containing sulfonate esters 2 were compared with their corresponding ortho-methylcarboxyphenyl sulfonates 3 and tosylates 4 (Table 1). In each case, substrates 2 reacted significantly faster than sulfonates 3. For example, the NALG derivative of 3-phenyl propanol (2a) reacted with LiCl to give 3-phenylpropyl chloride in 0.5 h and in 98% yield which was over 8 times faster than the reaction with the electronically similar 3a (Table 1, entries 1 and 2). Comparing the rates of reaction of 3a with 4a (entry 3) seems to indicate that the ortho-positioned ester of 3a confers a 4 to 5 fold rate enhancement. Thus, it is an advantage of the invention that the diethylene glycol unit of 2a is responsible for the additional 8 fold chloride addition rate enhancement of 2a relative to 3a. Furthermore, when the diethylene glycol unit of 2a was replaced with a linear hydrocarbon chain as in 5a (the hydrocarbon equivalent of the diethylene glycol unit of 2a), the substrate behaved similar to methyl ester derivative 3a (compare entries 2 and 4). Methylcarboxyphenyl sulfonates of secondary alcohols analogous to 3a were prepared (3b and 3c), however, these substrates failed to give the corresponding alkyl chloride product when reacted with LiCl. Instead, numerous unidentified side products were observed. Thus the chlorination rates of diethylene glycol-containing NALG derivatives of 1-phenyl-2-propanol and 4-decanol (2b and 2c) were compared with their corresponding tosylates 4b and 4c (entries 5-8). In both cases a significant rate enhancement was observed. For example tosylate 4c gave only a 5% conversion to the alkyl chloride after 24 h while NALG 2c gave the chloride product in 96% yield after only 6 hours (compare entries 7 and 8).