Collect. Czech. Chem. Commun. 1987, 52, 2035-2046

Hydroboration of 1-(5-hexenyl)piperidine and trans–1-(3-hexenyl)piperidine

Stanislav Kafka, Jan Kytner, Alexandra Šilhánková and Miloslav Ferles

Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6


1-(5-Hexenyl)piperidine (Ia) and trans-1-(3-hexenyl)piperidine (Ib) were hydroborated with tetrahydrofuran-borane, diborane in situ, 9-borabicyclo[3.3.1]nonane and triethylamine-borane. The hydroboration products were converted to 1-piperidinylhexanols IIa-IIe by hydrolysis with hydrochloric acid and subsequent oxidation with hydrogen peroxide in an alkaline medium. In addition to the alcohols IIa-IIe, the reaction also gave 1-hexylpiperidine (Ic). In the reactions with diborane in situ and triethylamine-borane, thermal isomerization of the hydroboration products was also studied. Hydroboration of Ia with triethylamine-borane afforded a mixture of spirocyclic amine-boranes IIIa-IIIc from which 6-(1-piperidinyl)-3-hexylboronic acid hydrochloride (IV) was obtained by hydrolysis with hydrochloric acid. Compounds IIIa-IIIc were slowly decomposed with ethanol to give esters of boronic acids Id-If. The synthesis of compounds Ia and Ib is described.