Nariyoshi Kawabata

Synthesis of cyclopropanes by the reaction of olefins with dialkylzinc and methylene iodide

Abstract A novel synthetic route to cyclopropanes by the reaction of olefins with dialkylzinc and methylene iodide is described. The essential feature of the reaction is similar to that of the Simmons-Smith reaction which involves the treatment of olefins with methylene iodide and zinc-copper couple. However, the novel route gives cyclopropanes more easily and is particularly suitable for the conversion of cationically polymerizable olefins such as vinyl ethers into the corresponding cyclopropanes. Olefins of this class, when the Simmons-Smith reaction is employed, sometimes give lower yields of cyclopropanes due to polymerization.

A novel synthesis of methylcyclopropanes

Abstract Several methylcyclopropanes have been prepared in 32–96% yield by the reaction of olefins with ethylidene iodide and diethylzinc. The reaction is electrophilic, and proceeds stereospecifically. In the case of the reaction with 1,2-disubstituted olefins, cis and trans olefins affords cyclopropane derivatives whose configurations with respect to the substituents from original olefins are cis and trans, respectively. The reaction yields predominantly the anti isomer from olefins containing the hydroxyl group such as allyl alcohol, 2-buten-1-ol and cyclopenten-4-ol. On the other hand, the syn isomer is obtained predominantly from other types of olefins. Stereochemistry of the reaction is discussed.

The relative reactivity of olefins in cycloaddition with zinc carbenoid

Abstract The relative reactivity of olefins was determined in the homogeneous reaction with zinc carbenoid generated from diethylzinc and CH2I2. The Hammett ϱ-value for substituted styrenes in this reaction was −1·61. The inductive effect was concluded to be the most influential factor which determines the relative reactivity of olefins in the reaction. The mechanism of the reaction is discussed in comparison with other carbene and carbenoid reactions.

Ring-expansion of aromatic compounds by methylcarbenoid of zinc and cadmium

Abstract Several 7-methylcyclohepta-1,3,5-triene derivatives have been prepared in 11–44% yield by the reaction of alkylbenzene and methylcarbenoid generated from ethylidene iodide with diethylzinc or diethylcadmium. The relative reactivity of alkylbenzene in this reaction was as follows: Benzene (0·4), toluene (1·0), ethylbenzene (1·2), cumene (1·0), o-xylene (2·1), p-xylene (2·0), and m-xylene (2·8). The relative reactivity showed a good correlationship with that in the Friedel—Crafts alkylation. Partial rate factors evaluated for the ring-expansion of toluene satisfied the selectivity relationship, log pfMe = 1·310 × log (pfMe/mfMe). Based on these results, the rate of the ring-expansion reaction was concluded to be determined by the σ-complex formation step. A stepwise mechanism was proposed for the reaction.

The reaction of organosilicon and organotin hydrides with zinc carbenoids generated fromd iethylzinc and geminal diiodoalkanes

The reaction of organosilicon hydrides with diethylzinc and methylene iodide or ethylidene iodide gave methyl- or ethylsilicon compounds in 61–83% yield, respectively. It is concluded that the reaction is an insertion of the methylene or ethylidene group into the siliconhydrogen bond. The relative reactivities of substituted phenyldimethylsilanes in this homogeneous reaction were investigated. The Hammett ϱ-values for the methylene and ethylidene insertions were −1.11 against σ0-values and −1.19 against σ-values, respectively. The mechanism of the reaction is discussed and compared with CCl2 and CH2 insertion into the siliconhydrogen bond via halomethylmercury compounds. On the other hand, the reaction of triethyltin hydride with diethylzinc and methylene iodide gave tetraethyltin as the major product and methyltriethyltin as a minor product. In the latter case, the reduction of organic iodide by the organotin hydride predominated over the insertion of the methylene group into the tinhydrogen bond.

Carbenoid reactions by means of diethylcadmium and gem-diiodoalkane

Abstract Cadmium carbenoid was prepared from diethylcadmium and gem -diiodoalkane and its reactions were investigated. Reaction of olefins with diethylcadmium and methylene iodide gave cyclopropanes in good yield by a stereospecific cis addition. Olefin, diethylcadmium and ethylidene iodide afforded Me substituted cyclopropane, in which the anti isomer was predominant contrary to the case of the corresponding reaction with diethylzinc. Phenylsubstituted cyclopropane was obtained from the reaction of olefin with diethylcadmium and benzal iodide. The reaction was found to favour the syn isomer but less than the corresponding reaction with diethylzinc. Phenylpropadienes were obtained from phenylacetylenes, diethylcadmium and gem -diiodoalkane. On the other hand, in the corresponding reaction with diethylzinc, metallation of acetylenic compound predominated over the formation of allene.