1-Pentanol reaction with thionyl chloride

Alkyl Chlorides. 3-Chloropentane was prepared by the reaction of thionyl chloride with 3-pentanol. Hexamethyl-phosphoric triamide, HMPT, was used as a complexing agent to ensure substitution at the 3 position (17). The organic layer was dried with magnesium sulfate and distilled. The middle fraction, b.p. 104°C, was collected for use. 1-Chloropentane was purified by repeated distillations. The above preparation procedures ensure maximum purity of the compounds for ESR study. 

Another interesting experiment repeats the reaction of a chiral alcohol with thionyl chloride, but an amine such as pyridine or triethylamine is added (see Chapter 26 for a discussion of amines). When (2i )-pentanol (105) reacts with thionyl chloride, but now in the presence of triethylamine, the 2-chloropentane product is isolated and has the 2S configuration, 108. The reaction occurs with inversion of configuration rather than retention of configuration, and this result suggests an Sn2 reaction. 

The 4,10,16-triaza-18-crown-6 macrocycle shown above was first prepared by Lehn and coworkers (Graf and Lehn, 1975 Lehn, 1985) and was an important intermediate for the synthesis of the first macrotetracyclic polyethers (Canceill et al., 1982 Kotzyba-Hibert et al., 1981 Pratt et al., 1988). The key step in this synthesis was conversion of A-tosyldiethanolamine [TsN(CH2CH20H)2] into the diacid dichloride, TsN(CH2CH20CH2C0Cl)2. As shown above, this conversion was accomplished by reaction with chlo-roacetic acid followed by oxalyl chloride (method A) (Miller et al., 1989) or by chloromethylation, sodium cyanide, hydrolysis and conversion of the diacid to the diacid dichloride (method B) (Graf and Lehn, 1981). The third hypothetical method to the diacid dichloride shown above starts with tosylamide and 5-chloro-3-oxa-l-pentanol followed by Jones oxidation and thionyl chloride (method C) (Qian et al., 1990). 

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