A new convenient synthesis of trisubstituted 1,3-dioxole-4-carboxylates from methyl 2-diazo-3-oxobutyrate and aldehydes

Ylide formation from the reaction of carbenes and carbenoids with heteroatom lone pairs

“…When the sulfur atom is substituted with a phenyl group, the reaction proceeds via a totally different pathway. Thus, treatment of 4-(phenylthio)-2-acetidinone (212) with copper powder in refluxing benzene afforded oxapenam 217 as the major product.15"17 The formation of this product also involves initial generation of sulfonium ylide 213 which is followed by successive cleavage of the C-S bond to produce 216 as a transient species. Subsequent ring closure by attack of the ketone oxygen on the iminium cation results in the formation of oxapenam 217.…”

Stereoselective Synthesis of α‐Diazo Oxime Ethers and Their Application in the Synthesis of Highly Substituted Pyrroles through a [3+2] Cycloaddition

“…Although it warrants further investigation, two plausible reaction pathways are shown. Path a involves metallotropy of a C-to N-metalated intermediate and subsequent nucleophilic addition to iminium ion E. [23] Alternatively, the intermediate B undergoes cyclopropanation to C, which then undergoes ring expansion (path b). [24] Finally, acid-promoted or thermal elimination of dimethylamine results in the formation of pyrrole.…”

Synthetic Applications of Carbonyl Ylides Generated via the Tandem Cyclization Cycloaddition Reaction of Rhodium Carbenoids

“…The activation energy associated with fragmentation of the ylide to singlet methylene and acetone was determined to be 45 kcal mol", Ibata and Liu 54 have employed chlorodiazirines as precursors for clectrophilic carbenes which react with aldehydes and ketones to form carbonyl ylides, One example involves the photolytic or thermal decomposition of 3chloro-3-p-nitrophenyldiazirine (47) in the presence of a mixture of acetone and dimethyl acctylenedicarboxylate to give dimethyl 2-hydroxy-5,5-dimcthyl-2-(p-nitrophenyl)-2,5-dihydrofuran-3,4-dicarboxylate (48). 40 hv -Reactions of carboalkoxycarbenes with carbonyl compounds have been described as early as 1885 41 and the structures of the dioxolane products were proposed in 1910. The fact that the reaction of the carbonyl ylide with an unsymmetrical dipolarophile givc<<; a 2:1 mixture of two rcgioisorners indicates that, in the HOMO of the carbonyl ylide, the electron density at the unsubstituted carbon is greater than that at the disubstitutcd carbon atom.…”