Titanium acetyl chloride

A solution of 1.0 mmol of 2-acetyl alkenoate in 2.5 mL of CH2C1, is added slowly to a solution of 4.0 mmol of titanium(IV) chloride in 7.5 mL of CH-CL under an atmosphere of nitrogen at — 78 °C. The mixture instantaneously turns deep red. and is stirred at — 78 °C before being quenched by the addition of 5 mL of sat. aq potassium carbonate. The mixture is then partitioned between 10 mL of bt20 and 10 mL of water. The aqueous phase is extracted with three 10-mL portions of Et2(), and the extracts are combined, washed with 10 mL of brine, and dried over anhyd potassium carbonate. Concentration under reduced pressure gives the crude product. Product analysis is by capillary GC. 

Chlorotriisopropoxytitanium7,31 is prepared either by the reaction of tetraisopropoxytitanium and acetyl chloride, or by mixing stoichiometric amounts of tetraisopropoxytitanium and titanium(IV) chloride31,32. By the latter method, a stock solution in hydrocarbon solvent, e.g., hexane, of known concentration can be prepared and used without distillation. 

Several modifications of the Simmons-Smith procedure have been developed in which an electrophile or Lewis acid is included. Inclusion of acetyl chloride accelerates the reaction and permits the use of dibromomethane.174 Titanium tetrachloride has similar effects in the reactions of unfunctionalized alkenes.175 Reactivity can be enhanced by inclusion of a small amount of trimethylsilyl chloride.176 The Simmons-Smith reaction has also been found to be sensitive to the purity of the zinc used. Electrolytically prepared zinc is much more reactive than zinc prepared by metallurgic smelting, and this has been traced to small amounts of lead in the latter material. 

Alternative methods for the formation of the catechol (5) were examined, and these serve to show other methods for introduction of the hydroxy group. Nitration of triene (6) followed by reduction to the amine and diazotization in the presence of methanol gave the phenol (8), but only in poor yield. The best method developed appears to be acetylation of the triene (6) with titanium tetrachloride/acetyl chloride to give the ketone (9), followed by Baeyer-Villiger oxidation to die acetate (10), which on hydrolysis afforded the catechol (8) in 70% overall yield. 

For synthesis of nucleosides, methyl 4-acetamido-2,3-di-0-benzoyl-4-deoxy-a-D-ribopyranoside (198c), obtained from 198a, was trans-formed by acetolysis into 4-acetamido-l,5-di-0-acetyl-2,3-di-0-benzoyl-4-deoxy-D-ribofuranose (199b). Either with preliminary treatment with hydrogen chloride in acetyl chloride, or directly, in the presence of titanium tetrachloride, 199b gave with chloromercuri-(6-... 

Low-valent metal salts have been used to bring about reductive cleavage of oximes. Corey and Rich-man used chromium(II) acetate to convert O-acetyl ketoximes into imines, which were hydrolyzed to ketones. " Aqueous titanium(III) chloride and vanadium(II) salts also reduce oximes again, the imines are usually hydrolyzed in situ, but some hindered imines, such as compound (37), are isolable." A method of preventing hydrolysis is to carry out the reduction in anhydrous conditions in the presence of an acylating agent. The products of such reactions, when applied to oximes of enolizable ketones, are en-amides. For example, these ketoximes are converted into A/-formylenamines when heated in acetonitrile with anhydrous titanium(III) acetate and acetic formic anhydride cyclohexanone oxime gives the en-amide (38 97% Scheme 22)." This type of reduction has been used by Barton and coworkers to prepare enamides from steroidal oximes. They reported that the reaction could be performed by acetic... 

Other methods used to improve the cyclopropanation in Simmons Smith reactions are ultrasonic cavitation and the use of catalytic amounts of titanium(IV) chloride to promote the reaction. A much better method is to use 1 mol% of acetyl chloride (based on zinc) and dibromo-methane in the presence of zinc dust and copper(I) chloride in diethyl ether. This system not only strongly accelerates alkene cyclopropanation, but also causes no special problems with Lewis acid sensitive substrates. Acetyl chloride works as a promoter by reacting with... 

A synthesis of the functionalized pyrrolidine 1131 makes use of an Eschenmoser sulfide contraction as the key step in the sequence (Scheme 165) [237]. The starting imide 1120 is readily prepared by sequential treatment of ( S)-malic acid with acetyl chloride, methyl amine, and acetyl chloride again. Protective and functional group manipulations afford 1123. Treatment of 1123 with allyItrimethylsilane and titanium tetrachloride gives 1124 in 72% yield, accompanied with 12% of the corresponding trans isomer. 

Valid for all substances which react violently with water, like the alkali metals (sodium and potassium) acetyl chloride, alkali alcoholates, boron trihalogen-ides, phosphorous tri- and pentahalogenides, sulfur chloride, titanium tetrachloride, or trichlorosilane. 

N,N,N, N -Tetramethyl-1,3-butanediamine Titanium acetylacetonate Triethylamine Zinc acetylacetonate catalyst, esterification Acetyl acetone Acetyl chloride Ammonium lactate Calcium acetate Cobalt diacetate Cumene sulfonic acid Ethylacetoacetate 2-Ethylhexyl titanate Fluoboric acid Lead acetate... 

Chloride coordination also seems to be present in the adducts of aluminium chloride and gallium(III) chloride s with acetyl chloride and in compounds of aluminium chloride or titanium(IV) chloride with mesitoyl chloride The corresponding compounds of acetyl chloride may also be considered to be ionic in character at least in solutions of liquid sulphur dioxide i-43 while those of benzoyl chloride are represented by coordination through the oxygen atom of the solvent, as has been shown for ClsSbOCClCeHs both by i.r.-measurements and an X-ray analysis . 

This type of facile reactivity was first observed in 1936 by Jennings eia/. who synthesized titanium monochloride triethoxide and dichloride diethoxide by the reactions of titanium tetraethoxide and acetyl chloride in the appropriate molar ratios. 

Previous works have shown that the diacetylation of acyclic olefins or paraffins leads to the formation of 6-diketones which cyclise to pyrylium salts. 31,32 YhQ formation of 2 is striking. We have noted that a solution of monoketone 1, acetyl chloride and aluminium chloride was stable at room temperature. Consequently, we assume that the formation of diketone 2 does not involve the acylation of monoketone but requires the acylation of the /3, T-unsaturated ketone (5-acetyl-1-methylcyclopentene) or related species. We also observed the rearrangement of the -acetylated dienolate 4 in presence of aluminium chloride or titanium tetrachloride at low temperature to diketone 2. There is an increasing evidence that unsaturated groups undergo the particularly easy 1,5-sigmatropic rearrangement. Moreover, the 1,5-acyl shift was subjected to catalysis by Lewis acids. But the possibility of an intramolecular process was conclusively ruled out by a cross-over experiment with propionyl chloride (overall yield 85-90 %). 

Rearrangement of the -acetylated dienolate 4 presents a wide scope and, like the Fries rearrangement, is polar. The plausible intermediates are titanium enolate and acetyl chloride. 

However, -silylated dienolates have not given any recognizable products with acetyl-chloride and titanium tetrachloride, see Fleming, I. Lee, T.V. Tetrahedron Lett. 1981, 22, 705. 

A comparison between three standard methods of synthesis of purine nucleosides, namely fusion, condensation of acetylated glycosyl chlorides, and from 1-acetates in the presence of titanium(iv) chloride has been made. Thus when the glucosaminyl acetate (1) was fused with theophylline in the presence of p-toluenesulphonic acid and p-nitrophenol, a 45 % yield of the nucleoside (2) was obtained. In contrast to the findings of Ishido et al. Carbohydrate Res., 1975, 44, 215), lower yields were obtained when the activating agents were omitted. The nucleoside (3) synthesized in 32 % yield from the glucosyl acetate... 

Also obtained (by-product) by reaction of acetyl chloride on o-cresol with aluminium chloride or titanium tetrachloride in nitrobenzene at 30-60° (3-6%) [2181,2600],... 

Also obtained by reaction of acetyl chloride with 2,6-di-tert-butylphenol in the presence of titanium tetrachloride [3816]. 

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