Catalyst, alumina boron trifluoride etherate

The thiol-epoxy reaction has proved to be an important synthetic tool in the preparation of a variety of pharmaceutical and natural products [55-64]. As mentioned above, this reaction can be performed using an acid or a base as a catalyst. The acid catalysts include boron trifluoride etherate [57], lanthanide chlorides [65], lithium perchlorate [60], cobalt chloride [66], and neutral alumina [67]. The basic catalysts can be organic or inorganic and include, among others, triethylamine, l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), tetra-n-butylammonium fluoride (TBAF), and LiOH [61-64, 68, 69]. In the literature on small molecules, it is important to note that this reaction is complete in a few minutes to a few hours of reaction time, with quantitative yields and with high regioselectivity. In the case of LiOH and TBAF, quantitative conversion of the epoxide to a desired thio-ether compound is observed within minutes and with 100% regioselectivity (isomer I) [68, 69]. 

Catalyst, alumina, 34, 79 35, 73 ammonium acetate, 31, 25, 27 boron trifluoride etherate, 38, 26 copper chromite, 31,32 36, 12 copper powder in quinoline for pyrolytic decarboxylation,... 

Indolizines with a saturated six-membered ring may be obtained from pyrrole or furan derivatives.225,226 The reaction of 3,4-dimethylpyrryl-magnesium bromide with y-chlorobutyronitrile followed by dilute acid gave 5,6,7,8-tetrahydro-l,2-dimethyl-5-oxoindolizine. 5,6,7,8-Tetrahy-droindolizine can be obtained by the cyclodehydration of 3-(2-furyl)-propylamine over alumina at 400°C. The same product is obtained by the treatment of 3-(2-pyrryl)propyl cyanide with hydrogen chloride in the presence of boron trifluoride etherate catalyst, followed by Wolff-Kishner reduction of the intermediate ketone. 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

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