Rearrangements trimethylsilyldiazomethane

The use of a carbene as the one-carbon component provides an alternative and efficient entry into the [4 + 2+1]-reaction manifold. Montgomery and Ni have developed a nickel-catalyzed process where the carbene is generated from trimethylsilyldiazomethane (Scheme 45).135 It is not known, however, if the seven-membered ring forms via a Cope rearrangement of a divinylcylopropane or if the metal is intimately involved in the step that leads directly to... 

Carriera and co-workers (287) described the 1,3-dipolar cycloaddition of trimethylsilyldiazomethane 171 with 165 (Note Opposite enantiomers are shown here). The intermediate 1-pyrazohne obtained from this reaction rearranged after acidic work up to furnish the 2-pyrazoltnes 172 with 80-88% de (Scheme 12.52). By further conversion of these products, optically active azaprolines were synthesized. 

The trimethylsilylynolate is prepared on treatment of trimethylsilyldiazomethane (23) with BuLi followed by exposure to carbon monoxide. The mechanism is explained by the fact that the lithiated silyldiazomethane (24) adds to carbon monoxide to give the labile a-diazoacyllithium 25, which rearranges to the ynolate 27 via the ketene intermediate 26 (equation 8). ... 

In the first step 21 is deprotonated with LDA to form lithium trimethylsilyldiazomethane (35), which attacks aldehyde 34 to give 36. Then 38 results via 37 by Peterson olefination under basic conditions. Next, 38 loses N2 to form carbene 39, which rearranges finally to the alkyne 40. Alkyne 22 was used without further purification in the next steps. 

A straight chain diazomethyl ketone will also undergo Wolff rearrangement on irradiation. Such diazomethyl ketones are readily prepared from the corresponding acid chloride (150) by exposure to diazomethane or, more conveniently, trimethylsilyldiazomethane (Petrarch). Tlie net one-carbon homologation so effected is known as the Amdt-Eistert synthesis. 

Reaction of ketones with lithium trimethylsilyldiazomethane 2 (Peterson olefination) to give after rearrangement the homologous alkynes. 

Thermal silylcarbene-to-silene rearrangements have been known for a long time1. The pyrolytic product from trimethylsilyldiazomethane, 1,1,2-trimethylsilene, was trapped in an argon matrix230, and the pyrolysis of bis(trimethylsilyl)diazomethane126 was reported to produce fair amounts of 2,4-bis(trimethylsilyl)hexamethyl-l,3-disilacyclobutane, the expected dimerization product of 2-(trimethylsilyl)-1,1,2-trimethylsilene. A second product was the disilane expected from an ene addition of one... 

Alkylative rearrangement Sulfonium ylide formation from allylic sulfides and diazo compounds (particularly trimethylsilyldiazomethane) and subsequent [2.3]sigma-tropic rearrangement are induced by (dppe)FeCl2 in 1,2-dichloroethane. 

Deprotonation of Trimethylsilyldiazomethane. Treatment of trimethylsilyldiazomethane with NaHMDS led efficiently to the formation of the corresponding sodium ion. Ring opening of A-carboxylated /3-lactams with this anion followed by photolytic Wolff rearrangement provided y-lactams in very good yields (eq 26). ... 

The ring-opening of W-alkoxycarbonylpyroglutamic acid esters 60 by lithium trimethylsilyldiazomethane at < -100 °C afforded diazo-norleucinates 61 with minimum formation of polymeric by-products. The Wolff rearrangement of 61 in the presence of silver benzoate in aqueous dioxane at 70 °C for 6 h led to the A-Boc a-ethyl ester of a-aminoadipic acid 62. With the use of ultrasound, the reaction proceeded at ambient temperature furnishing good yields of 62a-c. ... 

Addition of lithiated trimethylsilyldiazomethane to aldehydes provided adduct 103 which was shown through in situ IR measurements and quenching experiments to be in equilibrium with the 1,3-Brook-rearranged carbanion 104. Addition of methanol or methyl iodide provided 105 and 106, respectively. Stereocontrolled hydride shift upon formation of the rhodium-stabilized carbenoid provided (2)-selective formation of silyl enol ethers 107 and 108. ... 

The safe and stable diazomethane substitutes arylsulphonyldiazomethane and trimethylsilyldiazomethane have both been shown to be acylated by carboxylic acid chlorides. Subsequent Wolff rearrangement then provides new and safe alternatives for the Arndt-Eistert reaction (Scheme 59). 

From Epoxysilanes.—Epoxysilane rearrangements continue to provide useful routes to carbonyl compounds. For instance, homologation of a ketone to the corresponding aldehyde using lithium trimethylsilyldiazomethane (2) involves the intermediate formation and the subsequent hydrolysis of an a,/3-epoxysilane (3). Furthermore, it has been shown that pyrolysis of a,/8-epoxysilanes yields silyl enol ethers which, on hydrolysis, would give carbonyl compounds structurally isomeric to those which would be obtained by direct hydrolysis (Scheme 7). ... 

---