Cyclopropanes from Unsaturated Compounds, Methylene Iodide, and Zinc‐Copper Couple

Abstract

The reaction of the organozinc reagent prepared from methylene iodide and zinc‐copper couple with substituted unsaturated compounds has proved to be a versatile and convenient method for the synthesis of cyclopropanes. The synthesis is stereospecific with regard to the stereochemistry of the unsaturated compound and is usually free from serious side reactions; it can be carried out under mild conditions in diethyl and affords cyclopropanes often in good yields. This method can be easily adapted to large‐scale preparations. Two useful variations of the cyclopropanation reaction have appeared which involve the same or a similar organozinc intermediate: (1) diazomethane reacts with iodide in ether to form a reagent which converts unsaturated compounds to cyclopropanes; (2) methlyene iodide and diethyl zinc react in ether in the presence of unsaturated compounds to cyclopropanes. Processes are known in which a divalent carbon fragment adds to carbon‐carbon double bonds either as a free carbene or as an organometallic complex.

Selective edge functionalization of graphene layers with oxygenated groups by means of Reimer–Tiemann and domino Reimer–Tiemann/Cannizzaro reactions

“…For example, it was reported that by using the same reaction mixture, CHCl 3 in alkaline medium, in the presence of a phase transfer catalyst, cyclopropanation reaction occurs on alkenylic substrates [56] and at the edges of graphene layers [55]. These reagents are not the preferred ones for cyclopropanation, as cyclopropanes are traditionally formed by adding the methylene-zinc-iodide complex, generated from diethyl zinc and diiodomethane [57,58,79], or by transition metal-catalyzed decomposition of diazo compounds [59]. Moreover, cyclopropanation reaction was reported [55] to occur on the graphene layers in the presence of a phase transfer catalyst, which was not used in the work here reported.…”

“…By using the same reaction mixture, CHCl 3 in alkaline medium, in the presence of a phase transfer catalyst, cyclopropanation reaction occurs on alkenylic substrates [55] and at the edges of graphene layers [56]. These reagents are not the preferred ones, as cyclopropanes are traditionally formed by adding the methylene-zinc-iodide complex, generated from diethyl zinc and diiodomethane [57][58][59], or by transition metal-catalyzed decomposition of diazo compounds [60].…”

Structural Organozinc Chemistry

“…It has already been known for a long time that haloalkylzinc compounds are excellent reagents in cyclopropanation reactions 165 . Such compounds, however, are rather unstable and are usually prepared in situ.…”

Spiroannulated Cyclopropanes

“…The Simmons-Smith reaction, which involves cyclopropanation by the Zn-CH 2 I 2 system (equation 6), is a very popular variant of this method 22 . However, an application of the Simmons-Smith reaction to methylenecycloalkanes often requires the use of high excess (up to ten equivalents) of the reagent, which complicates the workup and lowers the yields.…”