Methylene reaction 4- butene

Diacetates of 1,4-butenediol derivatives are useful for double allylation to give cyclic compounds. l,4-Diacetoxy-2-butene (126) reacts with the cyclohexanone enamine 125 to give bicyclo[4.3.1]decenone (127) and vinylbicy-clo[3.2.1]octanone (128)[85,86]. The reaction of the 3-ketoglutarate 130 with cij-cyclopentene-3,5-diacetate (129) affords the furan derivative 131 [87]. The C- and 0-allylations of ambident lithium [(phenylsulfonyl)methylene]nitronate (132) with 129 give isoxazoline-2-oxide 133, which is converted into c -3-hydroxy-4-cyanocyclopentene (134)[S8]. Similarly, chiral m-3-amino-4-hyd-roxycyclopentene was prepared by the cyclization of yV-tosylcarbamate[89]. 

Like butadiene, allene undergoes dimerization and addition of nucleophiles to give 1-substituted 3-methyl-2-methylene-3-butenyl compounds. Dimerization-hydration of allene is catalyzed by Pd(0) in the presence of CO2 to give 3-methyl-2-methylene-3-buten-l-ol (1). An addition reaction with. MleOH proceeds without CO2 to give 2-methyl-4-methoxy-3-inethylene-1-butene (2)[1]. Similarly, piperidine reacts with allene to give the dimeric amine 3, and the reaction of malonate affords 4 in good yields. Pd(0) coordinated by maleic anhydride (MA) IS used as a catalyst[2]. 

A. Nucleophilic Attack on Carbon. —(/) Activated Olefins. A study of triarylphosphine-catalysed dimerization of acrylonitrile to 2-methylene-glutaronitrile (26) and 1,4-dicyano-l-butene (27) has established a balance between phosphine nucleophilicity and protolytic strength of the solvent. The reaction of methyl vinyl ketone with triphenylphosphine in triethyl-silanol gave only 3-methylene-2,6-heptadienone (28). 

However, coUisional deactivation in solution is so effective that no vibration-ally excited species is present. The reaction of photochemicaUy generated methylene with 2-methylpropene-l-)- C yields, 2-methyl-butene, which is formed by allylic insertion. In the liquid phase 2 % of the rearranged product labeled in the 3-position are formed, whereas in the gas phase 8% of this olefin can be isolated. This can be interpreted as follows 4% of 2-methyl-butene in solution and 16% of 2-methyl-butene in the gas phase are formed by an abstraction-recombination mechanism involving triplet methylene 96). 

In the photosensitized reaction of diazomethane which jdelds triplet methylene, a loss of stereospedfity is observed. However, with trans-2-butene cyclo-addition occmrs only to a limited extent. 

The preparation of acyclic allylic hydroperoxides has been described before (3, 7, 9), but it is not clear how the reactivities differ from the better known saturated hydroperoxides and cyclic allylic hydroperoxides. Dykstra and Mosher prepared allyl hydroperoxide by the reaction of allyl methanesulfonate with hydrogen peroxide and alcpholic potassium hydroxide and purified the hydroperoxide by gas chromatography. It detonated on heating and decomposed on exposure to light but was relatively stable in the cold and dark. The isomeric allylic hydroperoxides formed from the autoxidation of the branched olefin, 4-methyl-2-pentene, have also been isolated and were not abnormally reactive (3). In the present study, cis- and trans-2-butene were photooxidized in the presence of methylene blue as a sensitizer (14), and the product, l-butene-3-hydro-peroxide, was isolated by preparative chromatography. 1-Butene proved unreactive and 2-butene-l-hydroperoxide could be formed only by isomerization of the secondary hydroperoxide. 

The photosensitized oxidation of either trans-2-butene or a mixture of cis- and frans-2-butene in methanol using methylene blue as a sensitizer produced a single hydroperoxide—3-butene-2-hydroperoxide— cleanly at atmospheric pressure. The hydroperoxide was reduced to 3-butene-2-ol by treating the methanolic reaction solution with sodium... 

It has been assumed 42 that triplet CH2 does not undergo the insertion reaction with C—H bonds, but there is no firm evidence to support this contention. Reaction of CH2 with isobutene, cis and trans butene-2, and cyclohexene (see Sec. IV-E) under conditions favoring formation of triplet methylene gave relatively higher yields of C=C addition products, but the insertion products were nevertheless present in each case. We believe that reduced yields of the insertion products result from lower methylene energy rather than a fundamental difference in reaction mechanism. 

Although no absolute rates are available, the reaction of methylene with olefins is very fast. For example, Frey40 has shown that CH produced by CH2N2 photolysis (4358 A.) reacts with trans butene-2 at a rate 2.4 times slower than with CH2N2, and it is believed that the rate of reaction of CH2 with CH2N2 is comparable to the collision rate.64... 

Doering and Prinzbach20 photolyzed CH2N2 in the presence of 2-methylpropene 1-14C in the liquid phase and in the gas phase at 400 mm. The product ratios (Table II) in the liquid were quite similar to the high pressure values of Frey and Knox et al., although Doering and Prinzbach also report no 3-methylbutene-l. The chief object of this work was to study the mechanism of the insertion reaction of methylene into CH bonds. The product 2-methyl-butene-l, which is formed entirely by insertion and not by isomerization, was separated from the reaction... 

Butene-2. The experimental results for the reaction of methylene with cis and trans butene-2 are summarized in Table III. In the liquid phase and in the gas phase at high pressures (>200 mm.) the major products are 1,2-dimethylcyclopropane (addition to double bond), pentane-2, and 2-methylbutene-2 (insertion products), and the steric configuration of the butene-2 is predominantly retained in the products... 

The effect of added 02 can be explained by high deactivation efficiency of 02 toward the excited adducts and does not necessarily indicate reaction of 02 with triplet methylene or triplet intermediates. In fact, the overall results for added argon and added 02 can be explained by deactivation efficiencies in the ratio Ar butene-2 02 = 1 102-5 104-5. The results of both Frey and Anet42 and Anet et al.2 are from this point of view quite comparable with each other. We see that as we... 

If the metathesis polymerization is performed in solution, the preferred solvents are methylene chloride or chlorobenzene. Preferably, the solvent is aprotic in order to avoid ionic side reactions. The molecular weight is controlled by the addition of an acyclic olefin, such as 1-butene (13). 

There is a striking similarity in the behavior attributed to the triplet biradicals believed to be formed in the reactions of both triplet methylene and triplet oxygen with the 2-butenes. It should also be pointed out that in the triplet addition reactions of methylene, cis and trans olefins do not give the same cis and trans product ratios, indicating that the rate of spin inversion necessary for closure in the biradical intermediate occurs at a rate comparable to the rate of rotation about C—C bonds. 

Iodine-Mercury(II) oxide, 149 a-METHYLENE ALDEHYDES AND KETONES 1,4-Diazabicyclo[2.2.2]octane, 92 Dimethyl sulfoxide, 124 Formaldehyde, 136 Methoxyallene, 177 Methylene cycloalkanes By cyclization reactions Diacetatobis(triphenylphos-phine)palladium(II), 91 l-Hydroxy-3-trimethylsilylmethyl-3-butene, 147... 

Reactions of the recoil C1] with several olefins have been studied, including ethylene, propylene, cyclopentene, and cfs-butene-2, as well as with several paraffins. The type of products observed indicated the existence of several general modes of interaction, such as CH bond insertion, interactions with CC double bonds, formation of methylene-C11. The most important single product in all systems is acetylene, presumably formed by CH insertion and subsequent decomposition of the intermediate. Direct interaction with double bonds is shown by the fact that, for example, in the case of propylene, yields of stable carbon atom addition products were significantly higher than in the case of propane. The same was true for ethylene and ethane. 

In the 1,3,2-dioxaphosphole method a bis(2-butene-2,3-diyl) pyrophosphate is used as the condensing agent. It allows two successive esterifications of one phosphate group to be performed without additional activation. First a 5 -O-protected nucleoside is added in methylene chloride in the second reaction an unprotected nucleoside can be used, since only the 3 OH group is able to attack the cyclic enediol 3 -nucleosidyl phosphotriester. Protected dinucleoside triesters are obtained in 80% yield. Removals of protective groups, methoxytrityl by means of trifluoroacetic acid in methylene chloride and 1-methylacetonyl by aqueous triethyl-amine, also give about 80% yield (F. Ramirez, 1975, 1977). 

In a similar way, methylene moieties can be achieved by employing siliconeo-pentylmagnesium chloride (287) to carry out a methylenation 190. If 3-pentanone (257) is treated with 287,2-ethyl-1-butene (288) is formed (Scheme 39). For further applications of the Peterson reaction and its modification, see also64,191,192. ... 

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