Iminium-functionalized 1,2,3-triazoles by [3+2] cycloaddition reactions of internal acetylenic iminium triflates with organoazides
Author:
Tontsch Christian J.1, Gerster Holger1, Maas Gerhard2
Affiliation:
1. Institute of Organic Chemistry I , Ulm University , Albert-Einstein-Allee 11, D-89081 Ulm , Germany 2. Institute of Organic Chemistry I , Ulm University , Albert-Einstein-Allee 11, D-89081 Ulm , Germany , Fax: +49-731-5022803
Abstract
Abstract
Propyne iminium triflates 1–6 react as dipolarophiles in thermal [3 + 2]-cycloadditions with sufficiently electron rich organoazides to form 1,4,5-trisubstituted 1,2,3-triazoles with iminium functionalization. The reactions require rather strong thermal activation, but can be accelerated by microwave irradiation. The regioselectivity of the cycloaddition at the internal acetylenic bond of 3-cyclopropylpropyne and 3-arylpropyne iminium ions (1–3 and 4, respectively) is very high, but is lowered in the presence of sterically demanding substituents at the opposite end of the iminium-substituted C,C triple bond. The iminium-functionalized triazoles can easily be transformed into neutral compounds; herein reported is the formation of triazolyl ketones 10 by hydrolysis and of tertiary triazolyldimethyl amines 12 by LiAlH4 reduction. When the reduction is performed with sodium boranate or sodium cyanoboranate, amine–borane complexes 15 and 16 are obtained.
Publisher
Walter de Gruyter GmbH
Subject
General Chemistry
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