1- Acylimidazoles ketones

Organo copper and lithium enolates of cyclic ketones, lactones, and lactams or acyclic ketones are converted with acylimidazoles or imidazole-N-carboxylates into the corresponding / -diketones or / -ketoesters ... 

Acylimidazoles and 1-acyl-3,5-dimethylpyrazoles reacted with phenols and phenol ethers in the presence of AICI3 and at higher temperatures (110-120 °C) to give ketones in moderate yield.1"1... 

Unsaturated ketones.9 Allyltris(diethylamino)titanium (1) reacts with N-acylimidazoles (2) to give almost exclusively (3,7-unsaturated ketones (equation I). A similar reaction is observed with the crotyltris(diethylamino)titanium 3 (equation... 

When (253) reacts with phosgene the 1-acyl chloride product (254) can react with amines to give amides (79LA1756X while in a further transfer reaction with ketones the compounds (255) and (256) are produced (Scheme 146) (80H(14)97). Acylation of aromatic hydrocarbons using 1-acylimidazoles in the presence of trifluoracetic acid gives high yields provided that the aryl compounds are electron rich, e.g. p-dimethoxybenzene, thiophene, anisole <80BCJ1638). 

The 5-substituted 3-amino-l,2,4-oxadiazole (76) condensed with -di-ketones and /Fketoesters, giving the corresponding 3-enaminones (91). These compounds did not rearrange on melting, but with sodium ethoxide in DMF (a dipolar aprotic solvent which increased the nucleophilic power of anion 93) at 110°C they were converted into the 4-substituted 2-acylamino-5-acylimidazoles (92).60,61... 

The major classes of carbonyl compounds include aldehydes, ketones, carboxamides, esters, carboxylic acids and anhydrides, and carbonyl halides (acyl halides). These groups differ in the identity of the substituent X on the carbonyl group. At this point we concentrate on these examples, but a number of other carbonyl derivatives have important roles in synthetic and/or biological reactions. These other compounds include acyl cyanides, acyl azides, A-acylimidazoles, 0-aryl esters, and thioesters. The carbonyl compounds are arranged below in the order of the increasing reactivity toward nucleophilic addition. 

Aldehydes and Ketones from Carboxylic Acids. Reduction of the derived acylimidazole (2) with Lithium Aluminum Hydride achieves conversion of an aliphatic or aromatic carboxylic acid to an aldehyde (eq 6). DiisobutyUduminum Hydride has also been used, allowing preparation of a-acylamino aldehydes fromiV-protected amino acids. Similarly, reaction of... 

Reaction of acylimidazoles with the appropriate carbon nucleophile has also been used for the preparation of a-nitro ketones and /3-keto sulfoxides. 

C-Acylation of Active Methylene Compounds. Treatment of an acylimidazole, derived from a carboxylic acid and (1), with the magnesium salt of a malonic or methyhnalonic half thiol ester results in C-acylation under neutral conditions (eq 7)7 The presence of secondary hydroxyl functionality in the carboxylic acid is tolerated, but primary alcohols require protection. Magnesium salts of malonic esters may be used equally effectively. Intramolecular C-acylation of ketones has also been reported. ... 

Overall, this coupling substrate showed the greatest flexibility in the coupling of arene heterocycles with a wide variety of 3-substituted (Ri-substituted) A - Pr-substituted a,P-unsaturated 2-acylimidazoles. The resulting acyl imidazolides could be converted in straightforward fashion to either aldehyde, ketone, acid, ester, or amide moieties using a one-pot two- or three-reaction sequence (not shown in scheme). ... 

Reactions with 1-acylimidazoles Ketones from 1-acylimidazoles... 

Aryltrifluoromethyl ketones are prepared by reaction of an aryl-lithium with a,a,a-trifluoro-N,N-dimethylacetamide. 2-Acyloxypyridines and N-acylimidazoles, " in conjunction with trifluoroacetic acid, acylate arenes in good yield without the need for a classical Friedel-Crafts catalyst or a preformed mixed anhydride. However, imidazole in trifluoroacetic anhydride is reported to form 2-aryl-Af,JV -diacyl-4-imidazolines with arenes reactive towards electrophilic attack. These adducts are readily hydrolysed by sodium hydroxide to the corresponding aldehyde [equation (14)]. This sequence may offer advantages over the Vilsmeier method of formylation, in that the aldehyde is introduced in a protected form. 

Acylation of nitro-alkanes to give a-nitro-ketones is particularly efficient when acylimidazoles are used as the acylating agent. ... 

Stetter and Lorenz reported in 1985 that a thiazolylidine catalyst could promote the addition of a-ketoacid derivatives (17) to activated olefins (18) with loss of CO2 to give 1,4-diketones (19)7 The reaction has been called biomimetic because of its resemblance to the family of biochemical transformations effected by thiamine diphosphate-dependent enzymes acting on pyruvate While the original report was limited to alkyl vinyl ketones, more recent work by Scheldt and co-workers has greatly expanded the scope of this reaction by employing a, 3-unsaturated 2-acylimidazoles as the activated olefin component. ... 

Trost and coworkers extended their protocol to 2-acylimidazoles after accomplished enantioselective decarboxylative allylation of this type of ketones, the heterocycle was cleaved under formation of y,8-unsaturated esters. Thus, this protocol can be considered an equivalent of the enantioselective allylic alkylation of carboxylic esters [55a]. For the same purpose, the decarboxylative allylation of Af-acyloxazolinones was developed. The allylation products were converted, under cleavage of the heterocycle, into carboxylic acids, esters, and thioesters in high enantiomeric purity [55b]. 

Yoshida et aL recendy reported the direct synthesis of branched alkenylbo-rons via a-selective hydroboration of terminal alkynes employing (pin)B-B(dan) (where dan = 1,8-diaminonaphthalene) in the presence of 2 mol% [(SIPr)CuCl] 212,6 mol% KOt-Bu and MeOH (3 equiv.). Given that the scope of the alkynes is broad, the method was extended to the synthesis of Bexarotene and LG100268, which are used to treat T-cell lymphoma and as retinoid X receptor. In a different study by the same group, 208 catalyzed the selective addition of alkyl hydrob-oranes to imidazofyl-o,p-unsaturated ketones at the Imposition. Interestingly, the 2-acylimidazole moiety could be replaced by esters or amides. ... 

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