Isopropenyl methyl carbonate

Figure 1. Time plot of ion intensity in the 19-eV ICR spectrum of isopropenyl methyl carbonate at 8 x 10 7 torr with Me18OH at 1 x 10 6 torr. The numbers are m/z values. The horizontal scale represents 200 ms.

Linalool can be converted to geranyl acetone (63) by the CarroU reaction (34). By transesterification with ethyl acetoacetate, the intermediate ester thermally rearranges with loss of carbon dioxide. Linalool can also be converted to geranyl acetone by reaction with methyl isopropenyl ether. The linalyl isopropenyl ether rearranges to give the geranyl acetone. 

Two simple a, P-unsaturated acylsilanes, l-trimethylsilyl-2-propen-l-one (III) and l-trimethylsilyl-2-methyl-2-propen-l-one (IV) were chosen for polymerization studies. The polymerization of the carbon analogues of these a,p-unsaturated acylsilanes, that is, 4,4-dimethyl-2-propen-3-one (vinyl tert-butyl ketone, V) and 2,4,4-trimethyl-2-propen-3-one (isopropenyl tert-hutyl ketone, VI) has been studied by Willson et al. 16, IT), These authors reported that whereas V readily polymerizes under free-radical-polymerization conditions, VI undergoes polymerization only under anionic-initiation conditions in the presence of a crown ether as a complexing reagent. On the basis of UV and NMR spectroscopic data, Willson et al. (i6, 17) ascribed the difference in polymerization behavior to the nonplanar, unconjugated structure of ketone VI brought about by steric hindrance caused by the methyl group at C-2. 

Poly(vinyl ketones) such as poly(ethylene-a//-carbon monoxide) CAS 111190-67-1, poly(methyl vinyl ketone) CAS 25038-87-3, and poly(methyl isopropenyl ketone) CAS 25988-32-3, also have practical applications. For example, poly(ethylene-a/f-carbon monoxide) is used in photodegradable plastics and in various copolymers. Several studies were reported regarding the thermal stability of these polymers. It has been shown that poly(ethylene-a/f-carbon monoxide) decomposes upon heating with chain scission generating small molecular weight alkenes and ketones. Some literature reports discussing the thermal decomposition of poly(vinyl ketones) are summarized in Table 6.5.5 [13]. 

The dominant product ions from mixtures of methanol with methyl vinyl carbonate, methyl isopropenyl carbonate, and methyl tert-butyl carbonate are mlz 59, 73, and 73, respectively. In the case of the vinylic esters, ions mlz 59 and mlz 73 are each formed by two independent routes, decarboxylation and condensation of the protonated ester with methanol. Using deuterium and O-18-labeled methanol, we were able to unravel the reaction pathways involved. 

The precise requirements for the successful cycloaddition of alkenes to the carbon-nitrogen double bond remain uncertain, although various explanations have been advanced to account for the observed lack of reactivity.130 1,3-Di-methyl-6-azauracil and l,3-dimethyl-6-azathymine, however, undergo high-yield cycloaddition to a variety of alkenes including ethylene, tetramethylethylene, isobutylene, ethyl vinyl ether, vinyl acetate, and isopropenyl acetate. With ethyl vinyl ether and l,3-dimethyl-6-azauracil (160), for example, epimeric azetidines... 

Some abnormalities were reported in the initiations of methyl methacrylate polymerizations in toluene by butyllithium. Their nature is such that they suggest the possibility of more than one reaction taking place simultaneously. One, which must be the major one, is that of the oiganomet-allic compound reacting with the carbon-to-carbon double bond as shown above. The other, minor one, may be with the carbon-to-oxygen double bond. The major reaction produces methyl methacrylate anions. The minor reaction, however, yields butyl isopropenyl ketone with an accompanying formation of lithium methoxide ... 

To determine which carbon atom of the isopropenyl functionality in the azetidinone sulfinyl chloride participates in the ring closure, the above sequence of steps was repeated starting with the penicillin sulfoxide ester deuterated at the C-2 methyl position. The stereochemistry of this compound (70) had been previously established (Cooper, 1970). The NMR spectrum of the final product, methyl phthalimido-2-dideutero-3-methy-lenecepham-4-carboxylate (71), showed clearly a selective incorporation of deuterium at the C-2 position. It was, therefore, concluded that the olefinic carbon in the intermediary sulfinyl chloride was involved in the S—C-2 bond formation. 

A sulfinium cation (80) was suggested as a probable intermediate in the ring closure of sulfinyl chlorides by Lewis acids in an intramolecular ene reaction (Kukolja, 1977). The process is visualized as a complexation of the Lewis acid with either the oxygen or the chlorine atom of the sulfinyl chloride followed by formation of the S—C-2 bond with olefinic carbon, concomitant with hydrogen abstraction from the methyl group of the isopropenyl functionality (Scheme 4). In support of this mecha-... 

Linalool can be converted to geranyl acetone by the Carroll reaction (156). After transesterification with ethyl acetoacetate, the intermediate ester thermally rearranges with loss of carbon dioxide. Linalool can also be converted to geranyl acetone by reaction with methyl isopropenyl ether. The linalyl isopropenyl ether rearranges to give geranyl acetone. Geranyl acetone is an important intermediate in the synthesis of isophytol [505-32-8], famesol [106-28-5], and nerolidol [40716-66-3]. Isophytol is used in the manufacture of Vitamin E and thus linalool is a key intermediate in the synthesis of the latter. All of these reactions are shown in Fig. 8.55 in the section on nerolidol. 

Coupling of diazotized p-chloroaniline with 4-methyl- and with 4,6-dimethyl-pyrimidine occurs at the 4-methyl group, and not, as previously reported, at the 5-position. Pyrimidines bearing unsaturated carbon side-chains are uncommon species. Timely, therefore, are reports on the synthesis of the hitherto undescribed 2-isopropenyl-pyrimidines by dehydrobromination of 2-(2 -bromoprop-2 -yl)-pyrimidines and of 2-alkynyl-pyrimidines by coupling of 2-iodo-pyrimidines with monosubstituted alkynes in the presence of bis(tri-phenylphosphine)palladium(ii) chIoride[Pd(PPh3)Cl2] cuprous iodide, and tri-ethylamine. Nitration of some pyrimidine bases and nucleotides has been... 

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