From diazoketones

Photoelimination of nitrogen from diazoketones is complicated by Wolff rearrangement of the intermediate carbene, as shown below for diazoaceto-phenone<35) ... 

Participation of 69 in the reaction scheme would also explain why cyclopropanes are obtained from diazoacetic esters, but dihydrofurans from diazoketones 121 In the latter case, the enolate oxygen in 69 is more nucleophilic, thus favoring 1,5-over 1,3-ring closure. 

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]. 

Ketocarbenes generated from diazoketones give two main type of reactions. The first one is the conventional carbene reaction, i.e. intramolecular insertion into a C—H or C—C bond, as applied in the synthesis of a... 

Diiron enneacarbonyl, 50, 2J Diketones, from diazoketones and organoboranes, 53/ 82 3-DIKETONES FROM METHYL ALKYL KETONES 3-n-BUTYL-2,4-PENTANEDIONE, 51, 90 2,6-Dimethoxybenzaldehyde, by reduction of 2,6-dime thoxy-benzonitrile with Raney nickel alloy in formic acid,... 

ESTERIFICATION OF HINDERED ALCOHOLS tert-BUTYL p-TOLUATE, 51, 96 Esters, from diazoketones and organoboranes, 53, 82 Esters, a-deuterio-, 53, 82 Esters, y [Pg.59]

Wolffs synthesis of 1,2,3-thiadiazoles from diazoketones is also one of the earliest methods for forming this ring. Others have used this method with minor modifications to produce an array of... 

Nair et al. (87,88) achieved a synthesis of spirooxindole-containing molecules by adding isatins to various carbonyl ylides (Scheme 4.46). There has been relatively little research regarding the efficiency of C=0 of 1,2-dicarbonyl compounds as dipolarophiles relative to their olefinic counterparts. As anticipated, Nair found that the more electrophilic carbonyl of the isatin 187 (non-amide carbonyl) reacted smoothly with the carbonyl ylide formed from diazoketone 186 to give the spirocyclic adduct 188. Nair s yields were moderate to good (44—83%), but were based on recovered isatin. 

Thus far, in the alkaloid series discussed, the nitrogen atom has always been part of the core of the alkaloid strucmre, rather than acting in a dipolarophilic manner in the cycloaddition of the carbonyl ylide. Recently, Padwa et al. (117) addressed this deficiency by conducting model studies to synthesize the core of ribasine, an alkaloid containing the indanobenzazepine skeleton with a bridging ether moiety (Scheme 4.57). Padwa found that indeed it was possible to use a C = N 7i-bond as the dipolarophile. In the first generation, a substimted benzylidene imine (219) was added after formation of the putative carbonyl ylide from diazoketone 218. The result was formation of both the endo and exo adduct with the endo adduct favored in an 8 1 ratio. This indicates that the endo transition state was shghtly favored as dictated by symmetry controlled HOMO—LUMO interactions. 

When thiocarbonyl and ot-diazocarbonyl compounds are combined, acyl-substituted thiocarbonyl ylides 158 are generated from a nonisolable 3-acyl-1,2,4-thiadiazoline 157 (Scheme 8.36). In addition to giving acylthiiranes 159 and 1,3-dithiolanes 160, dipoles 158 can also 1,5-cyclize to produce 1,3-oxathioles 161. Acyl-thiocarbonyl ylides derived from diazoketones [e.g., HC(0)C(N2)R, R = Ph, f-Bu (219,220) 2-diazocyclohexanone (221)] produce 1,3-oxathioles [e.g., 162 (220), Scheme 8.36], while those derived from diazoesters (218,222,223) lead to thiiranes by 1,3-cyclization. Ylides derived from a-diazocarboxamides form 1,3-oxathioles (e.g., 163) and thiiranes (e.g., 159, R = f-Bu, R = NMePh, R = R" = Ph), depending on the nature of the substituents (220). A related 1,5-cyclization of an aminomethyl-thiocarbonyl ylide formed from dimethyl 3-anilino-2-diazobutanedioate was also reported (224). 

In situ generation of strained alkenes or alkynes requires photoelimination of a leaving group toward which the targeted product is unreactive. Thus, cycloalkynes may be generated by elimination of CO from cyclopropenones, but these must in turn be generated in situ (e.g., from diazoketones). The generation of ace-naphthyne (Scheme 17.10) may serve as an illustration of this procedure that did, however, not work for the parent cyclopentyne, a compound that still awaits spectroscopic characterization. 

The ambident nucleophilic character of enaminones is again demonstrated by the reaction with keto carbenes, produced in situ from diazoketones. Acyclic enaminones react via the -position to directly yield pyrroles (equation 11). Cyclic enaminones are shown to react at the nitrogen to give adducts which can be cyclized with KOH to... 

A stereoselective synthesis of aminoalkyl-substituted P-lactams (41) has been developed, the key step of which is [2+2] cycloaddition of imines to ketenes generated photochemically from diazoketones (42), which are derived from protected a-amino acids. A number of steroidal diazoketones related to progesterone have been synthesized as potential photoaffinity labelling reagents for the mineralocorticoid receptor. ... 

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