Nucleophilic reactions cyclopropane ring opening

The addition of nucleophiles to cyclic fluoroolefins has been reviewed by Park et al. [2 ]. The reaction with alcohols proceeds by addition-elimination to yield the cyclic vinylic ether, as illustrated by tlie reaction of l,2-dichloro-3,3-di-fluorocyclopropene Further reaction results in cyclopropane ring opening at the bond opposite the difluoromethylene carbon to give preferentially the methyl and ortho esters of (Z)-3-chloro-2-fluoroacrylic acid and a small amount of dimethyl malonate [29] (equation 8). 

Internal cyclopropane ring-opening reactions have also been developed using hydroxyl-substituted cyclopropanes. A typical example of this strategy comes from the reaction of the polycylic alcohol 131, which reacts quantitatively with Hg(OAc)2 to yield the acetal 132 (Equation (45)).165 Carbonate moieties can also be used as internal nucleophiles as, for example, in the case of 133, which affords 134 in a 60% yield upon reaction with Hg(OCOCF3) (Equation (46)).166... 

The mercury derivatives of bicyclic and monocyclic cyclopropanes underwent ready addition across electron-deficient C —C double bonds. This addition reaction was performed with isolation of the mercury intermediate, e.g. 6, giving and often without isolation of the mercury intermediate giving and 9 directly. Depending on the solvent used (MeOH or HOAc) either methoxide or acetate acted as the nucleophile in the ring-opening reaction. 

Depending on the reaction conditions, the allylic cation can be trapped by the halide ion expelled during cyclopropane ring opening or by an external nucleophile. For example, 3,3-dibromotricyclo[4.1.1.0 ]octane (14) rearranged to give 15. ... 

Cyclopropylphosphine oxides (140) react with the sodium salts of amides, presumably via cyclopropane ring-opening and intramolecular olefination, to give dihydropyrrole derivatives in moderate to good yield. Vicarious nucleophilic substitution reactions of a variety of substituted nitrobenzene derivatives with the carbanion of chloromethyldiphenylphosphine oxide to give o-(141) and p-(142)-nitrobenzyldiphenylphosphine oxides have been investigated. ... 

Selective ring opening of cyclopropanes. Ring opening by nucleophiles of suitably activated cyclopropanes has gained importance during recent years. Sodium or potassium cyanide can be used for this purpose. An example is the conversion of 1 or 2 into 3, ant/-7-cyano-eni/o-5-bromobicyclo[2.2.1]heptane-2-one, by reaction with potassium cyanide in the presence of catalytic amounts of sodium methoxide (equation T). The intermediate 2 can be isolated in high yield by reaction of 1 with 1 equiv. of sodium hexamethyldisilazide (4, 407) in ether. ... 

The allylic esters 189 and 191 conjugated with cyclopropane undergo regio-selective reactions without opening the cyclopropane ring. The soft carbon nucleophiles are introduced at the terminal carbon to give 190, and phenylation with phenylzinc chloride takes place on the cyclopropane ring to form 192[120]. 

The reactions of benzothiazinium salt 87d with nucleophiles such as PhSNa, PhSeNa, and KCl were examined (see Equation (24) and Table 13) <1997J(P1)309>. Treatment of 87d with PhSNa at 0°C for 2h provided vinyl cyclopropane 88d (82%) as the major product together with ring-opened product 90a (11%) (see entry 1). When the reaction was carried out with PhSeNa at —20 °C, and then warmed to room temperature, 90b was obtained in a higher yield (94%) with only trace of 88d being formed (see entry 2). Allyl chloride 90c was exclusively furnished by treatment of 87d with KCl in acetone at room temperature for 12 h (see entry 3). 

Various substituted cyclopropanes have been shown to undergo nucleophilic addition of alcoholic solvents. For example, the electron transfer reaction of phenylcyclopropane (43, R = H) with p-dicyanobenzene resulted in a ring-opened ether 44. This reaction also produced an aromatic substitution product (45, R = H) formed by coupling with the sensitizer anion. This reaction is the cyclopropane analog of the photo-NOCAS reaction, but preceded it by almost a decade. 

Sulfur ylides are among the most interesting carbon nucleophiles and their synthetic importance has been recently reviewed.One especially interesting use of these ylides is their application to the synthesis of cyclopropane derivatives using unsaturated oxazolones. For example, stabilized sulfur yhdes react with unsaturated oxazolones 629 via a Michael reaction to give oxazolone spirocyclopropanes 630 as shown in Scheme 7.202 and Table 7.46 (Fig. 7.57), whereas the less stabilized sulfur ylides give ring-opened products 631 as the major compounds (Scheme 7.202). ... 

Substituted cyclopropane systems also undergo nucleophilic addition of suitable solvents (MeOH). For example, the photoinduced ET reaction of 1,2-dimethyl-3-phenylcyclopropane (112, R = Me) with p-dicyanobenzene formed a ring-opened ether by anti-Markovnikov addition. The reaction occurs with essentially complete inversion of configuration at carbon, suggesting a nucleophilic cleavage of a one-electron cyclopropane bond, generating 113. The retention of chirality confirms that the stereochemistry of the parent molecule is unperturbed in the radical cation 112 " ". 

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