Alkynylcyclopropanes from Terminal Alkynes through Consecutive Coupling to Fischer Carbene Complexes and Selective Propargylene Transfer

Abstract

Fis(c)hing for cyclization! The sequential treatment of an acetylide with a Fischer carbene complex and an alkene/diene yields alkynylcyclopropanes with a wide substitution range. The intramolecular process provides 1‐alkynylbicyclo[3.1.0]cyclohexanes by starting from 1,6‐enynes. A non‐heteroatom‐stabilized metal alkynylcarbene is responsible for the selective transfer of the propargylene unit.

Divergent Gold‐Catalyzed Rearrangement of 1‐Alkenyl‐2‐alkynylcyclopropanes: Enyne Transformation Controlled by a Silicon Moiety

“…Continuing with our efforts to discover new mechanistic insights from gold-catalyzed 1,5-enyne rearrangements, we stirred a solution of 2-alkenyl-1alkynyl-1-silylcyclopropane 3, [9] which bears a silicon moiety attached to the bicyclic skeleton, in the presence of a gold(I) catalyst. Thus, treatment of compound 3 with a 5 mol% of IPrAuNTf 2 (IPr = 1,3bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-imidazol-2ylidene), in 1,2-dichloroethane at 25°C, resulted in its isomerization to alkynylcyclopropane 4, without for-mation of the expected alkynylcyclohexadiene 2 (Scheme 1).…”

Fischer Carbene Complexes: A Glance at Two Decades of Research on Higher‐Order Cycloaddition Reactions

“…The main characteristics of these low‐valent metal complexes is their electrophilic nature and remarkable instability [47,159,161] . Although the main applications of such complexes in organic synthesis are currently related to alkene and enyne metathesis, great interest exists in exploring a broader scope due to their unique reactivity [162–167] …”

Transition‐Metal‐Free Cascade Enyne Rearrangement and Cyclopropanation of Allenylphosphine Oxides with N‐Tosylhydrazones Accessing Alkynylcyclopropane Derivatives

“…The strategies can be classified as follows: a) direct cyclopropanation of terminal alkynes with cyclopropane sources (including methylenecyclo‐propanes, [6a] cyclopropanol, [6b,c] cyclopropenes, [6d–g] and cyclopropyl iodides [6h–j] ) in the presence of a transition metal; b) reactions between alkenes and alkynylcarbenes, which are generated from dihalogenated alkynes, [7a,b] alkynyldiazoacetates compounds, [7c–f] propargyl alcohols, [7g] and alkynyl Fischer‐Carbene‐Complexes (FCCs); [7h–l] c) [2+1] cycloaddition reactions of conjugated enynes with propargyl pivalate, [8a] N ‐tosylhydrazones, [8b–e] diazo compounds, [8f–l] (iodomethyl)‐zinc species, [8m] or sulfur ylides; [8n] d) intramolecular cyclopropanation of functionalized alkynes [9]…”