Furukawa modification

In 1992 Kobayashi et al. [47] reported the first catalytic and enantioselective cyclo-propanation using the Furukawa modification [48] of the Simmons-Smith reaction of allylic alcohols in the presence of a chiral bis(sulfonamide)-Zn complex, prepared in-situ from the bis(sulfonamide) 63 and diethylzinc. When cinnamyl alcohol 62 was treated with EtgZn (2 equiv.), CHgIg (3 equiv.), and the bis(sulfonamide) 63 (12 mol %) in dichloromethane at -23 °C, the corresponding cyclopropane 64 was obtained in 82 % yield with 76 % ee (Sch. 26). They proposed a transition state XXIII (Fig. 5) in which the chiral zinc complex interacts with the oxygen atom of the allylic alkoxide and the iodine atom of iodomethylzinc moiety. They also reported the use of the bis(sulfonamide)-alkylaluminum complex 65 as the Lewis acidic component catalyzing the Simmons-Smith reaction [49]. 

There are a number of modifications of this reaction all providing the same product Furukawa s Reagent EtjZn + ICH2I (1 1)... 

A number of modifications of the original Simmons-Smith cyclopropanation procedure have been reported. Furukawa s reagent, (iodomethyl)zinc derived from diethylzinc and diiodomethane, ° or its modification using chloroiodomethane instead of diiodomethane, ° allows more flexibility in the choice of solvent. The reagent is homogeneous and the cyclopropanation of olefins can be carried out in non-complexing solvents, such as dichloromethane or 1,2-dichloroethane, which greatly increase the reactivity of the zinc carbenoids. 

A similar system was studied by Furukawa and Saegusa10). These authors found that modification of the initiating system with an amine considerably increases the yield of the high molecular weight polymer and concluded therefore that a coordinative anionic mechanism operates in the system. 

Pathway A). Indeed, it was this method that Simmons and Smith first used in their seminal study, with many methods of zinc activation available (see 1.4.5.1). Furukawa s modification of the reaction uses diethyl zinc, and proceeds via alkyl ligand exchange to give 8 (Pathway B). Finally, Wittig reported the insertion of diazomethane (7) into zinc iodide to give 6, although this method is not widely used. 

Modifications to the Ziegler-Natta catalyst system have led to the preparation of alternating copolymers from olefins, such as ethylene and propylene, and diolefins, such as butadiene and isoprene. In typical systems (Furukawa 1972, 1974a, b) the catalyst is prepared at very low temperatures (-70°C or below) from three components a... 

Preparative Methods for the synthesis of the parent and the 2-monoalkyl-substituted compounds, reduction of ethyl 3-chloropropionate with sodium-potassium alloy in the presence of chlorotrimethylsilane in ether. A recent modification using ultrasound irradiation is much more convenient and more widely applicable. Other substituted derivatives are prepared by cyclopropanation of alkyl silyl ketene acetals with the Furukawa reagent (diiodomethane/diethylzinc). ... 

Salts, oxides, organometallic derivatives of divalent and triva-lent metals are the most usual stereospecific initiators used both for oxiranes and thiiranes. Many of them were already described in reviews (1-6). The most studied of them result from modification reactions of organometallic compounds such as ZnEt the hydrolysis of which was described by Furukawa, Tsuruta (1959 and Colclough (1964), the alcoolysis mainly studied by Tsuruta... 

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