Chloro borane-dimethyl sulfide

Chloro(thexyl)borane Dimethyl Sulfide, 144 C9HF11O4S2... 

The synthetic route to iV-aryl [3.2.2] cryptands 5a and 5b is shown in the Scheme. Starting from the A-aryl diethanolamine, reaction with two equivalents of chloro-acetic and /-BuOK in t-BuOH followed by conversion of the diacid to the diester for purification gave la and lb in yields of 49 and 25%, respectively. Subsequent acid-catalyzed hydrolysis produced the dicarboxylic acid amine hydrochlorides 2a and 2b quantitatively. Attempts to form the diacid chloride of 2a resulted in an unreactive deep blue-colored substance of unknown identity. Ring closure was effected by adaptation of a method from peptide synthesis [8]. Mixed anhydrides 3a and 3b formed by reaction with two equivalents of isobutyl chloroformate in the presence of triethylamine were cyclized with l,10-diaza-18-crown-6 in toluene to produce the corresponding cryptand diamides 4a and 4b in 36 and 32% yields, respectively. Reduction with borane-dimethyl sulfide in THF provided 74% yields of 5a and 5b. 

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