O-Diazoketones

The diverse chemistry of carbenes is beyond the scope of this account, but a few typical reactions are shown here to illustrate the usefulness of the photochemical generation of these reactive species. A carbene can insert into a C—H bond, and this finds application in the reaction of an a-diazoamide to produce a P-lactam (5.29). Carbenes derived from o-diazoketones can rearrange to ketenes, and thus a route is opened up to ring-contraction for making more highly strained systems <5.301. Carbenes also react with alkenes, often by cycloaddition to yield cyclopropanes in a process that can be very efficient (5.31) and highly stereoselective (5.321. 

Yates found active MnO, superior to mercuric oxide for oxidation of 1-mesityl-glyoxal-2-hydrazone to the o-diazoketone with mercuric oxide the yield was only... 

An interesting application of carbenoid O/H insertion is the synthesis of macrocyclic oxacrown ethers 337 from a,(o-diazoketones 336 and oligoethylene glycols... 

It is possible to formylate o -diazoketones, albeit in usually poor yield, by keeping the reaction mixture between —10 and room temperature one of the better yields is shown in Eq. 93b. ... 

Tanigaki, K. and Ebbesen, T.W., Dynamics of the Wolff Rearrangement of Six-Membered Ring O-Diazoketones by Laser Flash Photolysis,/. Phys. Chem., 93,4531, 1989. 

A solution of 0.38 g of the diazoketone in 2 ml of acetic acid is heated 0.5 hr at 100-105°. Removal of the solvent under reduced pressure and crystallization of the residue from acetone-ether gives 0.27 g of 1 la,21-dihydroxy-pregn-4-ene-3,20-dione 11,21-diacetate mp, 144-146° [a]o 156° (CHCI3). An additional 60 mg of this product is obtained by chromatography of the mother liquor (total yield 72%). 

Diazoketones react with trifluoromcthyl hypofluorite to give a mixture of a,a-difluoro ketones and o-fluoro-a-trifluoromethoxy ketones [70, 71] With elemental fluorine, two fluorine atoms replace the nitrogen in both diazoketones and unactivated diazo eompounds [70, 72, 73] (equation 9)... 

The synthesis of /Mactams from diazoketones and imines can be realized not only by using photochemical reaction conditions but also under the action of microwave irradiation. When the reaction was performed in o-dichlorobenzene at 180 °C, however, the rates of thermal and microwave-assisted formations of -lactams were shown to be identical within the limits of experimental error (80-85% conversion after 5 min) [30]. 

The reaction232-235 (see also Ref. 236) of 1-diazoketones with hydrogen fluoride that affords 1-fluoro ketones has also been applied to carbohydrates, with, however, no success. Treatment of 3,4-di-O-benzoyl-1-deoxy-l-diazo-D-gfycero-tetrulose with hydrogen fluoride in ether mainly afforded 3,4-di-O-benzoyl-D-gfycero-tetrulose, whereas, with hydrogen bromide and chloride, 3,4-di-O-benzoyl-l-bromo-l-deoxy-and 3,4-di-O-benzoyl-l-chloro-l-deoxy-D-gfycero-tetrulose, respec-... 

Sebacid acid dinitrile, 50, 20 SELECTIVE o-BROMINATION OF AN ARALKYL KETONE WITH PHENYL-TRIMETHYL AMMONIUM TRIBROMIDE 2-BRQM0ACETYL-6-METH-OXYNAPHTHALENE AND 2,2-DI-BROMOACETYL-6-METHOXYNAPH-THALENE, 53, 111 Shikimic acid, 50, 27 Silver benzoate, as catalyst in decomposition of diazoketones, 50, 78... 

A broad range of compounds can be O-alkylated with carbene complexes, including primary, secondary, and tertiary alcohols, phenols, enols, hemiaminals, hydroxylamines, carboxylic acids, dialkyl phosphates, etc. When either strongly acidic substrates [1214] and/or sensitive carbene precursors are used (e.g. aliphatic diazoalkanes [1215] or diazoketones) etherification can occur spontaneously without the need for any catalyst, or upon catalysis by Lewis acids [1216]. 

Substituted norbornane derivatives have been synthesized by the reaction of norbornenes with carbonyl ylides derived from a-diazoketones by a 1,3-dipolar cycloaddition route (Equation 97) <2002TL5981>. These reactions occur in high yields and with excellent o o-selectivity (Table 8). 

Other stable diazoalkanes, such as diazoketones, can also be converted into halogen derivatives, as illustrated by the conversion of 3,4-di-O-benzoyl-l-deoxy-l-diazo-D-g/t/cero-tetrulose into the 1-bromo- and 1-chloro-deoxy derivatives by the action of hydrogen bromide and hydrogen chloride, respectively.196... 

Azoles of types 62 and 64 are isomeric with the open-chain compounds 61 and 63, respectively. Rearrangement between the two is rapid, and the thermodynamically stable isomer is encountered. Thus diazoketones 61 (X = O) exist as such, but diazothioketones 61 (X = S) spontaneously ring close to thiadiazoles 62 (X = S). 1,2,3-Triazoles generally... 

Illudin M (46), a toxic sesquiterpene isolated from the jack-o -lantem mushroom, has been synthesized via the same tandem cyclization-cycloaddition strategy involving a-diazoketone 55. The first and key step of the synthesis consisted of a carbonyl ylide 1,3-... 

Rearrangement to acids is accomplished by adding a dioxane solution of diazoketone to a suspension of silver oxide in warm aqueous sodium thiosulfate solution. Examples include biphenyl-2-acetic acid (86%), ° 1-ace-naphthylacetic acid (64%), decane-1,10-dicarboxylic acid (72%), and o-bromophenylacetic acid (63%). ... 

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