Boron trifluoride-acetic anhydride

The course of acid-catalyzed acetylations with acetic anhydride may depend markedly on the concentration of the acid and the type of acid. Reaction of 7-(3-deoxy-3-nitro-/3-D-galactopyrano-syl)theophylline with acetic anhydride in the presence of one molar equivalent of perchloric acid gave the 2, 4, 6 -triacetate in 89% yield, but, in the presence of only a trace of the acid, 82% of the 4, 6 -diacetate was obtained.93 Treatment of the manno isomer of the nucleoside with acetic anhydride-boron trifluoride gave the 4, 6 -diacetate as a crystalline product (24%), whereas phosphoric acid as the catalyst yielded the 2, 4, 6 -triester (45%). 

The dehydration of thiobenzoylthioglycolic acid (135, R = Ph, R = H) with acetic anhydride-boron trifluoride was initially described as yielding the meso-ionic l,3-dithiol-4-one (134, R = Ph, R = H), but subsequent studies showed that the product was in fact the 5-substituted derivative 134, R = Ph, R = COCHjSCSPh. Authentic meso-ionic l,3-dithiol-4-ones (134) have recently been prepared (85-90% yield) by the cyclodehydration of the acids (135) with acetic anhydride-triethylamine at 0°-10°. Examples include anhydro-4-hydroxy-2-phenyl-l,3-dithiolium hydroxide (134, R = Ph, R = H) described as scarlet needles, m.p. 113°—115° this compound is sensitive to moisture. Anhydro-4-hydroxy-2,5-diphenyl-1,3-dithiolium hydroxide (134, R = R = Ph) was obtained as gold lustered, deep violet needles,... 

Several catalysts have been recommended for the N-acetylation of carbazole with acetic anhydride boron trifluoride, phosphorus pentoxide, concentrated sulfuric acid, zinc chloride, and phosphoric acid all gave 9-acetylcarbazole in moderate to good yield. 9-Acetylcarbazole can also be prepared using the Vilsmeier complex of N,N-dimethylacetamide and phosgene. ... 

ACETYLATION Acetic anhydride-Boron trifluoride etherate Alumina. 

The desired elimination predominated only when the 3a-6romo-compound (55) was reduced with zinc, giving the 19-acetoxy-2-ene (56). A 3-oxo-2jS, 19-ether is opened by acetic anhydride-boron trifluoride to give the 2o,19-diacetoxy-ketone. Inversion at C-2 may occur either through nucleophilic attack of... 

Thus the double bond may be either cyclic or exocyclic to a ring, and the silyl group on a ring substituent or on a ring. Silacyclopentene derivatives also may be acetylated, either with acetyl chloride/ aluminum chloride or acetic anhydride/boron trifluoride, with retention of the silyl group (equation 19). ... 

C-19 methyl migration occurs in the presence of acetic anhydride-boron trifluoride etherate. Prolonged hydrolysis, followed by selective reacetylation of the C-3 hydroxyl and Jones oxidation, yielded the cucurbitone (48). 

Annulene undergoes addition reactions with bromine or with maleic anhydride thus its simple chemistry differs markedly from that of benzene [16]. Under special conditions it gives reactions which provide products typical of electrophilic substitution, but these reactions may not proceed by straightforward electrophilic substitution mechanisms. Thus it may be acetylated with acetic anhydride - boron trifluoride [52], and nitrated with copper(ll) nitrate in acetic anhydride, giving a mixture of dinitro-isomers [52,53]. Pyridinium bromide perbromide provided either monobromo-... 

Related Reagents. Boron Trifluoride-Acetic Acid Boron Trifluoride-Acetic Anhydride Boron Trifluoride Etherate Boron Trifluoride Dimethyl Sulfide Tetrafluoroboric Acid. 

Cleavage of aliphatic ethers occurs with the reaction of acetic anhydride, boron trifluoride etherate, and lithiumbromide (eq 46). The ethers are cleaved to the corresponding acetoxy compounds contaminated with a small amount of unsaturated product. In some cases, the lithium halide may not be necessary. 

A cyclopropyl ketone is subject to homoconjugate addition using acetic anhydride/boron trifluoride etherate. Upon acetate addition, the enol is trapped as its enol acetate (eq 53). ... 

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