Cyclo general reactivity

Diazomalonic esters, in their behavior towards enol ethers, fit neither into the general reactivity pattern of 2-diazo-l,3-dicarbonyl compounds nor into that of alkyl diazoacetates. With the enol ethers in Scheme 17, no dihydrofurans are obtained as was the case with 2-diazo-l,3-dicarbonyl compounds. Rather, copper-induced cyclo-propanation yielding 70 occurs with ethoxymethylene cyclohexane u4). However,... 

General Reactivity.—Deamination of 1-aminocyclohexanemethanol (221) gave (222) (56 %), together with (223) (24 %) and smaller amounts of cyclo-... 

Dienes are generally much less reactive when coordinated to transition metals than when in an uncoordinated state. An important discovery was thus made by Fischer and Fischer (86) in 1960 when they found that cyclo-hexadiene-iron tricarbonyl (XV) (formed from 1,3-cyclohexadiene and iron pentacarbonyl) undergoes hydride ion abstraction by triphenylmethyl tetrafluoroborate to form 7r-cyclohexadienyl-iron tricarbonyl tetra-fluoroborate (XVI) ... 

Some exceptions to the general rules occur. Cyclopentene is completely combusted, undoubtedly because of the high reactivity of cyclo-pentadiene. 4,4-Dimethyl-1-pentene is expected to produce an unsaturated aldehyde, but instead 2,3-dimethylpentadiene is the initial product. A methyl shift from a quarternary carbon is apparently easy, permitting formation of a diene instead of the oxygenated compound. 3,3-Dimethyl-l-butene is not expected to react at all under the general rules, but here also a methyl shift occurs so that diene, olefin aldehyde, diene aldehyde, and diene dialdehyde are formed. The reactivity of the latter olefin relative to 1-butene, measured by oxidation of a mixture at low conversion, was 0.21, while that of 4,4-dimethyl-1-pentene was 0.75. These reactivities suggest that isomerization occurs before reaction for 3,3-dimethyl-l-butene, while isomerization probably occurs after the aUyl intermediate is formed in the case of the pentene. 

Micellar effects upon chemical equihbria in aqueous solution were recognized many years ago, and Hartley [12] explained them in terms of the ability of ionic micelles to attract counterions and repel coions. This general explanation was subsequently applied to micellar effects upon chemical reactivity in aqueous solution [13]. A very important monograph outlined the state of knowledge up to 1974, and also noted other associated species which could influence the rates of thermal, photochemical and radiation induced reactions [1]. The initial studies of micellar effects were made in water, but subsequently micelle-like aggregates were observed in non-aqueous solution. These aggregates can also influence chemical reactivity. In some respects the effects of micelles on reactivity are similar to those of cyclo-dextrins or synthetic polyelectrolytes. 

Reactive Intermediates.—Additions of dichlorocarbene to cyclo-octatetraene, bicyclo-[6,l,0]nona-2,4,6-triene, iV-ethoxycarbonylazepine, cycloheptatriene, and related compounds have been studied, and the stereochemistry of the products explained in terms of approach of the carbene from the least hindered direction, e.g. cyclo-octatetraene gave only one bis-adduct (172). Treatment of cyclo-octene with 1,1-dichloroethane and n-butyl-lithium gave 9-chloro-9-methylbicyclo[6,l,0]nonane, which was converted into 9-methylenebicyclo[6,l,0]nonane using potassium t-butoxide this procedure has been developed into a general preparation of methylene-cyclopropanes. ... 

Simple Diels-Alder Additions.—The [4 + 2] and reverse-[4 + 2] cycloaddition reactions of species containing C=X bonds (X = P, As, Sb, Bi, Si, Ge, etc.) have been discussed and the evidence reviewed.The general chemical reactivities of cyclo-propenones and triafulvenes, including their behaviour in Diels-Alder reactions, have been broadly summarized. Kagi and Johnson have reported extensive studies on the Diels-Alder reactions between cyclopropene and various chloro-cyclopentadienes in which endo-adducts are obtained, selective dechlorination, hydrolysis and other reactions of these adducts, and H n.m.r. spectral correlations. 

The related cyclo >entadienylmolybdenum complexes appear to have similar reactivity. The 2-butyne complex thus gave ds-2-butene as the only organic product upon treatment with hydrogen chloride at low temperature (Thomas, 1973). The generality of this reaction has not been demonstrated. 

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