Preparation of Vinylcyclopropanes by Sodium Mediated Reductive Isomerization of Methylenecyclopropanes

Abstract

We disclosed therein a new reaction of reductive isomerization of methylenecyclopropanes (MCPs) to vinylcyclopropanes (VCPs). On treatment with sodium metal in liquid ammonia, MCPs bearing a C-O bond at allylic position undergo both a reductive cleavage of the C-O bond and an isomerization of the C-C double bond giving rise to VCPs. The scope of the reductive isomerization was investigated and showed a broad applicability since various functional groups are tolerated. MCP substrates were straightforwardly prepared by a palladium-promoted [2 + 1] cycloaddition between norbornene derivatives with alkynes.

[2+1] Cycloaddition Affording Methylene- and Vinylidenecyclopropane Derivatives: A Journey around the Reactivity of Metal-Phosphinito-Phosphinous Acid Complexes

“…Only ethyl phenylphosphinate 3f allowed the formation of ACP, but in low yield along with many byproducts (Table , entry 8). Using the catalytic system Pd(OAc) 2 and PhCyP(O)H 3d , the scope of the [2+1] cycloaddition was particularly broad ,. As depicted in Scheme , various ACPs could be prepared in moderate to quantitative yields.…”

“…During the project directed toward the study of the platinum‐mediated [3+2] cycloaddition with ACPs that did not contain the bicyclo[2.2.1]heptane moiety, we discovered an unusual reactivity of ACPs. As an alternative to ethenolysis, the reductive cleavage of the nitrogen–nitrogen bond of cyclic hydrazines was investigated . Among the several methodologies reported to carry out the reductive N–N cleavage of hydrazines, we chose to study the one involving the use of sodium metal in liquid ammonia.…”

“…Using the catalytic system Pd(OAc) 2 and PhCyP(O)H 3d, the scope of the [2 + 1] cycloaddition was particularly broad. [7,13] As depicted in Scheme 6, various ACPs could be prepared in moderate to quantitative yields. There is a good tolerance to various functional groups, such as ethers, alcohols, sulfones, amines, and nitriles.…”

“…As an alternative to ethenolysis, the reductive cleavage of the nitrogen-nitrogen bond of cyclic hydrazines was investigated. [13] Among the several methodologies reported to carry out the reductive N-N cleavage of hydrazines, we chose to study the one involving the use of sodium metal in liquid ammonia. When ACP 4n was treated with Na (2.5 equiv), the formation of the expected product 28n was not detected (Scheme 27).…”

Synergistic NaBH4 Reduction/Cyclization of 2‐Aroylcyclopropane‐1‐carboxylates: Synthesis of 3‐Oxabicyclo[3.1.0]hexane Derivatives

“…The great pharmaceutical potential of this scaffold prompted us to search for new and efficient methods that would provide diversified structures in a minimum number of steps. As a result of their biological importance, many methods for the construction of 3‐oxabicyclo[3.1.0]hexanes have been developed 3‐Oxabicyclo[3.1.0]hexanes can be synthesized by various strategies, such as the Ireland–Claisen rearrangement procedure,, intramolecular cyclization reactions of aryldiazoacetates, Ru‐catalysed annulations, Pd‐promoted [2+1] cycloaddition reactions between dihydrofuran derivatives and alkynes, or Au‐catalysed cyclopropanation reactions of substituted (allyloxy)sulfonium ylides . Another interesting synthetic pathway, reported by Pathak and co‐worker, is based on the formation of single diastereomers of substituted 3‐oxabicyclo[3.1.0]hexanes through the reaction of the corresponding vinyl selenone with nitromethane, malononitrile, and dimethyl malonate in the presence of t BuOK in THF at room temperature .…”