Trifluoroborane

The regioselectivity of the addition of terminal alkynes to epoxides is improved, when the reagents prepared from the lithiated alkynes and either trifluoroborane or chlorodiethyl-aluminum arc employed (M. Yamaguchi, 1983 S. Danishefsky, 1976). (Ethoxyethynyl)lithium-trifluoroborane (1 1) is a convenient reagent for converting epoxides to y-lactones (M. Naka-tsuka, 1990 see p. 327f. cf. S. Danishefsky, 1976). 

Boron trifluoride [7637-07-2] (trifluoroborane), BF, was first reported in 1809 by Gay-Lussac and Thenard (1) who prepared it by the reaction of boric acid and fluorspar at duU red heat. It is a colorless gas when dry, but fumes in the presence of moisture yielding a dense white smoke of irritating, pungent odor. It is widely used as an acid catalyst (2) for many types of organic reactions, especially for the production of polymer and petroleum (qv) products. The gas was first produced commercially in 1936 by the Harshaw Chemical Co. (see also Boron COMPOUNDS). 

Compounds containing fluorine and chlorine are also donors to BF3. Aqueous fluoroboric acid and the tetrafluoroborates of metals, nonmetals, and organic radicals represent a large class of compounds in which the fluoride ion is coordinating with trifluoroborane. Representative examples of these compounds are given in Table 5. Coordination compounds of boron trifluoride with the chlorides of sodium, aluminum, iron, copper, 2inc, tin, and lead have been indicated (53) they are probably chlorotrifluoroborates. 

Trifluoroborane may form adducts with some of the transition elements. See Reference 54 for a detailed discussion of complexes of trifluoroborane with various Group 6—10 (VI, VII, and VIII) species. 

Boron trifluoride is also employed in nuclear technology by uti1i2ing several nuclear characteristics of the boron atom. Of the two isotopes, B and B, only B has a significant absorption cross section for thermal neutrons. It is used in " BF as a neutron-absorbing medium in proportional neutron counters and for controlling nuclear reactors (qv). Some of the complexes of trifluoroborane have been used for the separation of the boron isotopes and the enrichment of B as (84). 

Nonchelation control also results from the trifluoroborane-mediated addition of the following silylketcne acetal to 2-thioaldehydes. The diastereomeric ratios of the adducts surpasses 98 2... 

Boron trifluoride etherate Ethyl ether, compd. with boron fluoride (BF3) (1 1) (8) Ethane, 1,1-oxybis-, compd. with trifluoroborane (1 1) (9) (109-63-7)... 

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