2,6-ди-трет-бутил-4-метилпиридин

Химические свойства

light yellow powder

Использование

2,6-Di-tert-butyl-4-methylpyridine is used for the generation of enol triflates from ketones using trifluoromethanesulfonic anhydride. It is also used in the synthesis of 1,2-dihydro-2-silanaphthalene derivatives, as base in PtCl4-catalyzed cyclization reactions of homopropargyl azide derivatives and in diastereoselective synthesis of β-thiomannopyranosides.

Общее описание

2,6-Di-tert-butyl-4-methylpyridine is a sterically hindered, non-nucleophilic base which distinguishes between protonic and Lewis acids. It also enables the direct high-yield conversion of aldehydes and ketones to vinyl triflates. It inhibits desilylation and hydration of the products during GaCl₃-catalyzed ortho-ethynylation of phenol.

Методы очистки

A possible impurity is 2,6-di-tert-butyl-4-neopentylpyridine. Attempts to remove coloured impurities directly by distillation, acid-base extraction or treatment with activated charcoal were unsuccessful. Pure material is obtained by dissolving 0.3mole of the alkylpyridine in pentane (150mL) and introducing it at the top of a cold water jacketed chromatographic column (40 x 4.5cm) (cooling is necessary because the base in pentane reacts exothermically with alumina) containing activated and acidic alumina (300g). The column is eluted with pentane using a 1L constant pressure funnel fitted at the top of the column to provide slight pressure. All the pyridine is obtained in the first two litres of eluent (the progress of elution is monitored by spotting a fluorescent TLC plate and examining under short wave UV light—a dark blue spot is evidence for the presence of the alkylpyridine). Elution is complete in 1hour. Pentane is removed on a rotovap with 90-93% recovery yielding a liquid which solidifies on cooling, m 31-32o, and the base can be distilled. The HPtCl6 salt has m 213-314o(dec), and the CF3SO3H salt has m 202.5-203.5o (from CH2Cl2). [Anderson & Stang Org Synth Coll Vol VII 144 1981, Beilstein 20/6 V 190.]