Carbonyl group, insertion into 77-’-carbene

Acyclic and cyclic allylic ethers and acetals react normally with dihalocarbenes at the C=C bond [e.g. 77, 85, 108,114,121,122], Carbene insertion into the C=C bond of allylic ketones, which can be complicated by competitive reaction by the carbonyl group, can also be effected via the initial formation of the acetal and has been used in the synthesis of cyclonona-3,4- and -4,5-dienones from cyclooctenones [125],... 

Because these insertion reactions create new bonds at completely unfunctionalized centres, they can be very useful in synthesis. This next carbene is created between two carbonyl groups from a diazocompound with rhodium catalysis and selectively inserts into a C-H bond five atoms away to form a substituted cyclopentanonc. 

The conversion of the carbonyl group of an 7V,7V-disubstituted 2-aminoketone to an alkylidene carbene leads to insertion of the carbene into one of the nitrogen substituents and the formation of a five-membered ring at the oxidation level of a dihydropyrrole. Manganese dioxide readily converts such species (or indeed pyrrolidines ) into the aromatic pyrroles. ... 

Nitrenes, like carbenes, are immensely reactive and electrophilic, and the same Wolff-style migration (insertion into an adjacent C—C bond) takes place in which the substituent R migrates from carbon to the electron-deficient nitrogen atom of the nitrene. The product is an isocyanate. Isocyanates are unstable to hydrolysis attack by water on the carbonyl group gives a carbamlc acid, which decomposes to an amine. Alternatively, reaction with an alcohol gives a carbamate. If the alcohol is BnOH, the product is a Cbz-protected amine. 

A second functionalization approach was based on the insertion of carbenes into the C-H bond (Scheme 3). The reaction of different polyolefins, such as high density polyethylene (HDPE), atactic polypropylene (aPP), isotactic polypropylene (iPP), ethylene-propylene copolymers (EP) and polyisobutene (iPBu) with diazoesters at 210T in bulk has been shown to give a product containing the carboxylate functionality attached to the polymer backbone. The presence of the functional groups in the polymer was inferred by IR spectroscopy (carbonyl stretching band at 1740 cm "1 and in case of chloroethyldiazoacetate... 

Earlier, we observed that diazomethane reacts with MA at 20 C to yield a ring-enlarged lactone 27 due to carbene insertion into the OC—O bond of the anhydride. It has been observed that trimethylsilyl azide (TMSA) instead inserts into the bond between the olefinic carbon and carbonyl grouping. No triazoline derivative was reported. Washburne et utilized this reaction to synthesize oxauracils. They treated MA with TMSA to obtain the silyl derivative 41 which could be converted to oxauracil 42 in a 60-80% overall... 

Carbonyl carbenes insert into various X—H bonds (X = O, N, C) in the presence of rhodium carboxylates. An application of the insertion of carbalkoxy carbene into the OH group of alcohols is illustrated by a synthesis of chorismic acid [104]. 

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