Abstract
Isoprenylation of aldehydes and ketones was directly performed by selective indium insertion on a mixture of 2-bromomethyl-1,3-butadiene and its vinylic isomers in good yields. A short synthesis of (±)-ipsenol, an aggregation pheromone of the Ips paraconfusus bark beetle, demonstrates the utility of this method in organic synthesis.
Highlights
The introduction of isoprene unit into various compounds presents an important problem in organic synthesis, since isoprene derivatives with conjugated diene system are widely distributed in nature
Fallis and coworkers have established that treatment of 5-bromo-1,3pentadiene 1 with indium metal, in the presence of aldehydes and ketones, results in γ-pentadienylation to generate 1,4-diene as 4, with excellent regioselectivity and respectable yields.[4]
Isoprenylation processes can be achieved from allylic anions 6, which can be generated from direct metalation of 2-bromomethyl-1,3-butadiene 5, to afford 7 in the presence of aldehydes and ketones. 6-13 Several metals, such as Zn,[7,8,9,10,11,12] Cr(II)[13] etc, have been used for this purpose
Summary
The introduction of isoprene unit into various compounds (isoprenylation) presents an important problem in organic synthesis, since isoprene derivatives with conjugated diene system are widely distributed in nature. Fallis and coworkers have established that treatment of 5-bromo-1,3pentadiene 1 with indium metal, in the presence of aldehydes and ketones, results in γ-pentadienylation to generate 1,4-diene as 4, with excellent regioselectivity and respectable yields.[4]
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