Cleavage acetyl chloride

More useful than the preceding methods is cleavage of alkoxides by acetyl chloride or bromide. One, two, three, or four alkoxyls can be replaced by chloride or bromide. Benzoyl chloride gives poor yields, however. The tri- and tetrachlorides, which are stronger Lewis acids than mono- and dichlorides, coordinate with the alkyl acetate formed and yield distillable complexes (46,55,56). 

Acetyl chloride, SmCl3, pentane, rt, 15 min-24 h, 89-96% yield." The efficiency of dioxolane cleavage is very poor under these conditions. 

The acetate derivative of alkaloid uleine (104) obtained from its N-oxide 103 with acetyl chloride also undergoes cleavage by sodium borohydiide, giving carbazole 105 in high yield (85LA2073 Scheme 29). 

Ultraviolet irradiation of oxadiazoline (38d) at 333.6 nm (or irradiation using benzophenone as a triplet sensitiser) gave 2-diazopropane and methyl acetate. A triplet biradical intermediate formed by cleavage of the C(OMe)—N bond was postulated <90TL863>. Oxadiazolinone (42) underwent nucleophilic attack at the carbonyl group by methyllithium to give acetate (41) after treatment of the product with acetyl chloride <89CJC1753>. 

The use of acetyl chloride instead of acetic anhydride without Lewis acid for the cleavage of the ether bond at 10 to 15° allowed the isolation of the chloromethyl methylnitrosamine XI in 15-20% yields after two distillations (15,16). 

However, these synthetic procedures were useful only in the preparation of primary a-acetoxymethyl alkylnitrosamines and a-chloromethyl alkylnitrosamines. The cleavage of secondary ethers, such as XIII with acetic anhydride or acetyl chloride was so vigorous that no characterizable substances could be isolated. In view of this problem, we looked for another synthetic route which would allow the isolation of secondary derivatives. The first experiment tried, namely that of nitrosyl chloride with N-methylene t-butylamine at -30° was successful. The addition of NOCl at this temperature... 

Acetyl chloride/methanol has often been employed by Hove for cleaving the silyl protecting group. Mechanistically one can postulate that reaction of the acid chloride with methanol leads to an ether solution of anhydrous hydrogen chloride, which then effects the cleavage. 

Trimethylsilylbutadiene 140 is treated with acetyl chloride at — 80 °C to give the adducts, which are dehydrochlorinated to give 141 (equation 117)209. No carbon-silicon bond cleavage is observed. 

Thionolactones A method for conversion of lactones into the corresponding thionolactones involves first conversion of the lactone into the N,N-dimethyl-iminolactonium tetrafluoroborate (4) by a method used by Deslongchamps et al. Treatment of the salt 4 with sodium hydrosulfide in acetone at -78° for about 1 hour and then with acetyl chloride and pyridine (to trap the dimethylamine) results in the thionolactone 5. The low yield of 5 when n = 4 results mainly from cleavage to AcO(CH2)4C(=S)N(CH3)2. 

Although cyclopropanes are far less reactive than alkenes, they can be opened by various electrophiles including protic acids, bromine, chlorine, mercury(II) salts and acetyl chloride. The ring-cleavage processes of cyclopropanes by electrophiles were studied with the aid of ab initio molecular orbital and other calculations. Early studies assumed that traditional... 

Most trialkylhalogermanes are conveniently prepared by the selective cleavage of one alkyl group of tetraorganogermanes with halogens, hydrogen halides, or acetyl chloride in the presence of aluminum chloride (eq (87)) [84]. 

Polymer-bound chiral hydrazines have been synthesized to furnish a-branched amides (Scheme 12.17) [13, 23], Enantiopure (i-methoxyamines 37 and 38, derived from readily available hydroxyproline and N,N-dibenzylleucinol, respectively, have been attached to solid support and transformed into the corresponding hydrazine auxiliaries 39 and 40 via several steps. The synthesis of a series of enantiomerically enriched a-branched amides required the coupling of aliphatic and aromatic aldehydes to form hydrazones 41 and 42 followed by the addition of different nucleophiles. Cleavage of the N-N bond of the resulting hydrazines 43 and 44 led to a-branched amines 45. Further conversion with benzoyl chloride or acetyl chloride furnished amides 46 in yields of 24—51% and 50-83% ee. 

B5hme procedure involving cleavage of JV -tetramethyl(methylene)diamine (34) with TMS-I. Qeavage of (34) with acetyl chloride in analogy to the Bdhme procedure furnishes the crystalline chloride (31), as does cleavage of methyl dimethylaminomethyl ether with methyltrichlorosilane. The trifluoroacetate (32), unlike the iodide or chloride, is a liquid and is prepared by Polonovski reaction of... 

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