Boron trifluoride ethanate

Selectivity in formation of protective groups may also be achieved by a proper choice of reaction conditions and catalyst. Thus formation of the 3-monothioketal from 3,6-diketones is achieved by dilution of the ethane-dithiol-boron trifluoride reaction mixture with acetic acid. 3-Monocyanohydrins are obtained in good yield from 3,20-diketo-(5a)-pregnanes by diluting the exchange reaction with ethanol. Similarly, dilution of the... 

Thioketals are readily formed by acid-catalyzed reaction with ethane-dithiol. Selective thioketal formation is achieved at C-3 in the presence of a 6-ketone by carrying out the boron trifluoride catalyzed reaction in diluted medium. Selective protection of the 3-carbonyl group as a thioketal has been effected in high yield with A" -3,17-diketones, A" -3,20-diketones and A" -3,l 1,17-triones in acetic acid at room temperature in the presence of p-toluenesulfonic acid. In the case of thioketals the double bond remains in the 4,5-position. This result is attributed to the greater nucleophilicity of sulfur as compared to oxygen, which promotes closure of intermediate (66) to the protonated cyclic mercaptal (67) rather than elimination to the 3,5-diene [cf. ketal (70) via intermediates (68) and (69)]." " ... 

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)... 

Treatment of l-[2-(2-methoxy-5-isopropylphenyl)-l-hydroxyethyl]-2,6,6-tri-methylcyclohexene with triethylsilane and boron trifluoride etherate in dichloro-methane at —10° leads to its reduction to 2-(2,6,6-trimethyl-l-cyclohexenyl)-l-(2-methoxy-5-isopropylphenyl)ethane in 69% yield (Eq. 36).174... 

The submitters employed 75 g. (0.5 mole) of the liquid 1 2 boron trifluoride-acetic acid complex obtained from Harshaw Chemical Company. Since the checkers were unable to obtain this complex from a commercial source, they prepared the solid 1 1 complex following published directions.3 4 A 2-1. threenecked flask is fitted with a mechanical stirrer, a gas outlet tube, and a gas inlet tube extending to the bottom of the flask. A solution of 230 ml. of acetic acid in 750 ml. of 1,2-dichloro-ethane is added to the flask and a stream of boron trifluoride gas is passed through the reaction flask while the solution is stirred and cooled with an ice bath. After approximately 1 hour, when the mixture is saturated, the addition of boron trifluoride is stopped and the insoluble 1 1 boron trifluoride-acetic acid complex is rapidly collected on a filter, washed with 200 ml. of... 

Bi s (tri methyl si lyloxy )cyclobut-l-ene Silane, (1 -cyclobuten-1,2-ylenedioxy)bis[trimethyl- Silane, [1-cyclobutene-1,2-diylbis(oxy)]bis[trimethy1- (17082-61-0), 65, 17 Boron trifluoride etherate Ethyl ether, compd. with boron fluoride (BFj) (1 1) Ethane, 1,1 -oxybis-, compd. with trifluoroborane (1 1) (109-63-7), 65, 17... 

The 6,7-dihydro-5/f -1,4-dioxepin (266) has been prepared (54CR(38)982). and more recently it has been shown that the 2,3-dihydro-5jF/-l,4-dioxepins (263) and (265) can be produced from 1,4-dioxine-halocarbene adducts (264), either by heating under reflux in xylene or by treatment with bases. The allylic chlorine atom in (263) is readily substituted by alkoxide or cyanide ions (77ZC331, 76UKZ968). Saturated rings of type (267) have been prepared by the treatment of cyclic acetals of ethane-1,2-diol with vinyl ethers in the presence of boron trifluoride, and l,4-dioxepan-5-one (268) has been prepared by the reaction of bromoform and silver nitrate with aqueous dioxane (60AG415). 

The stoichiometric equivalents of halofluorides have been recently applied to transform alkylene dithioacetals into gcm-difluorides.70-71 Dithioacetals such as 1,3-dithiolanes and 1,3-dithianes arc readily obtained from the corresponding carbonyl compounds by the reaction with ethane-1,2-dithiol or propane-1,3-dithiol in the presence of the complexes boron trifluoride-bis(acetic acid) or boron trifluoride-diethyl ether. Using a two-step procedure, a range of aldehydes and ketones can be converted into gem-difluorides under mild conditions. 

The reaction of aldehydes or ketones with ethane-1,2-dithiol or propane-1,3-dithiol to form 1,3-dithiolanes or 1,3-dithianes is an important reaction, as these compounds under suitable conditions are acyl anion equivalents (see Section 5.9, p. 626). These cyclic dithioacetals have been less used as protective groups, though when required are formed in high yield in the presence of boron trifluoride-etherate.138... 

Boron trifluoride etherate Ethyl ether, compd. with boron fluoride (1 1) (8) Ethane,... 

The formation of thioacetals from aldehydes and ketones involves the reaction with a thiol such as ethane-1,2-dithiol in the presence of a Lewis acid catalyst such as boron trifluoride eiherate. These derivatives have been described earlier. 

---