Methylenecycloalkanes reactions

The Simmons-Smith reaction, which involves cyclopropanation by the Zn CH2I2 system (equation 6), is a very popular variant of this method22. 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. 

Single, transient triazoline intermediates are also considered to be formed in the reactions of methylenecycloalkanes with cyanogen azides,190-192 although again, cyclopropylidenecyclohexane gives rise to a mixture of the regioisomeric triazoline intermediates.191... 

Kinetic investigation of the reaction of (p-anisyl)phenylcarbenium tetrachloroborate with methylenecycloalkanes (ring size 3-12 and 15) exhibits correlation of the second-order rate constants with the solvolysis rates of the corresponding cycloalkyl derivatives382. 

The high diastereoselectivities and mildness of these reaction conditions should make this reaction valuable for the synthesis of quaternary carbon centres and exo-methylenecycloalkanes. 

The first report of an aryllithum carbolithiation reaction is due to Woolsey and coworkers14, who reported the cyclization reaction of o-(3-butenyl)bromobenzene via the aryllithium derivative (Scheme 3). More recently, Bailey and coworkers have studied the carbolithiation reaction of aryllithiums tethered to a methylenecycloalkane 291 (Scheme... 

Although many recent improvements in the preparation of the Simmons-Smith reagent might be helpfuP , the authors of this chapter would recommend one to consider an alternative two-step cyclopropanation procedure, which includes cycloaddition of dichloro- or dibromocarbene to methylenecycloalkane followed by reductive dehalo-genation (equation if. The first reaction is usually carried under phase transfer conditions and presents a very simple and efficient procedure. Reduction of gem-dihalocyclopropanes with lithium in rerr-butanol or with sodium in liquid ammonia usually proceeds without complications and with high yield. 

Polymerization of Spiro[2.n]alkanes. Spiro[2.6]nonane (M5), spiro [2.7]decane (M(i), and spiro[2.1 ljtetradecane (M7) were prepared from the corresponding methylenecycloalkanes (methylenecycloheptane, meth-ylenecyclooctane, and methylenecyclododecane, respectively) by the Simmons and Smith reaction (14) see Equation 8. 

The yield varies from 40 to 60% no matter what size the ring is. The separation of the alkenes and their derivatives is difficult because of the closeness of their boiling points. Furthermore, one obtains, probably as the result of partial isomerization during reaction of the methylenecycloalkanes to 1-methylcycloalkenes, small amounts of secondary compounds, such as the corresponding methylbicyclo[n.l.O] alkanes. 

Cyclizations. A great number of substrates designed for cyclization have been studied, including those leading to l-sulfinylmethylene-2-methylenecycloalkanes and to pyrroles. - Intramolecular Heck reaction involving enol triflate and allylsilane moieties is useful for the synthesis of cyclic compounds. ... 

Methylenecycloalkane-l-methanols J Activation with McjAlCl makes formaldehyde (from paraformaldehyde) receptive to attack by 1-trimethylsilyl-methylcycloalkenes in the presence of SnCl. The reaction is a silicon-directed ene reaction. 

Most of the published kinetic data on base-catalyzed alkene isomerizations are for reactions of I-alkenes. Alkyl substitution stabilizes alkenes and products of isomerization of terminal alkenes isomerize at slower rates than their precursors. Rates of isomerization of methylcycloalkenes can be estimated from kinetic and equilibrium data or measured directly These compounds isomerize at slower rates than the corresponding methylenecycloalkanes, as expected. 

The reaction proceeds normally with 5- or 6-membered 1-methylcycloalkenes 33, 36 (or for better yields with the isomeric methylenecycloalkanes 34, 37). In the case of 6-membered rings, the products (35) may be converted by dehydrogenation into benzo[6]pyrylium salts and then isoquinolines. 

The catalysts precursors A and B contain no Ru carbene at the outset of the reaction. Thus, the question arises whether the cycloisomerization of the allyl propargyl ethers reported above proceeds via a metathesis pathway or another type of mechanism (see Section 2). To try to answer this question, a catalytic transformation of dienes was attempted with the catalytic system B, A complete conversion of the starting dienes into the cycloisomerization methylenecycloalkane derivatives 71-74, isolated in 64-88%, was observed... 

Methylenecycloalkanes have been found to undergo a regioselective, palladium-catalyzed hydrocarboxylation reaction with formic acid and carbon monoxide to give cycloalkylacetic acids in good yield. In the case of camphene, carbon monoxide pressures of 40 atm are required to achieve satisfactory conversions (eq 99). ... 

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