2-Methyl-2-propen

Chemically, wood tar is a complex mixture that contains at least 200 individual compounds, among which the foUowing have been isolated (1) 2-methoxyphenol, 2-methoxy-4-ethylphenol, 5-meth5i-2-methoxyphenol, 2,6-x5ienol, butyric acid, crotonic acid, 1-hydroxy-2-propanone, butyrolactone, 2-methyl-3-hydroxy-4JT-pyran-4-one, 2-methyl-2-propenal, methyl ethyl ketone, methyl isopropyl ketone, methyl furyl ketone, and 2-hydroxy-3-methyl-2-cyclopenten-l-one. 

Methyl-2-propen-l-ol, purchased from Aldrich Chemical Company, was distilled from anhydrous potassium carbonate. It was added directly to the n-butyllithium solution using a long needle. The checkers quickly replaced the pressure-equalizing dropping funnel with a serum cap to carry out this addition. The funnel was fitted to a small dry flask to prevent the introduction of moisture during the addition period and replaced on the reaction flask immediately afterwards. 

Dianion formation from 2-methyl-2-propen-l-ol seems to be highly dependent on reaction conditions. Silylation of the dianion generated using a previously reported method was unsuccessful in our hands. The procedure described here for the metalation of the allylic alcohol is a modification of the one reported for formation of the dianion of 3-methyl-3-buten-l-ol The critical variant appears to be the polarity of the reaction medium. In solvents such as ether and hexane, substantial amounts (15-50%) of the vinyl-silane 3 are observed. Very poor yields of the desired product were obtained in dirnethoxyethane and hexamethylphosphoric triamide, presumably because of the decomposition of these solvents under these conditions. Empirically, the optimal solvent seems to be a mixture of ether and tetrahydrofuran in a ratio (v/v) varying from 1.4 to 2.2 in this case 3 becomes a very minor component. 

Table 1.6.1. Epoxidation of 2-methyl-2-propene-l-ol benefieial effeets of eatalytie reaetions and derivatization.

In general, 2-substituted allylic alcohols are epoxidized in good enantioselectivity. Like glycidol, however, the product epoxides are susceptible to ring opening via nucleophilic attack at the C-3 position. Results of the AE reaction on 2-methyl-2-propene-l-ol followed by derivatization of the resulting epoxy alcohol are shown in Table 1.6.1. Other examples are shown below. 

Z)-l-Methyl-2-butenylboronate 7 undergoes an exceptionally enantioselective reaction with benzaldehyde (99% ee), propanal (79%. 98% ee), 2-methyl-2-propenal (85%, 99% ee), and ( )-2-methyl-2-pentenal (81 %, 99% ee)10 38. Excellent enantioselectivity is also realized in reactions of the analogous chiral a-methyl-) y-disubstituted allylboronate27 40. Whether the l,2-dicyclohexyl-l,2-ethanediol auxiliary plays a beneficial role in this reaction, as suggested above for the asymmetric allylboration reactions of 6, has not yet been determined. 

The lithium derivative of di-f-butylfluorosilyl-2,6-diisopropylphenyl-amine reacts with 2-methyl-2-propenal in two competing ways. In a [2 + 4] cycloaddition, an oxa-3-aza-2-sila-5-cyclohexene is formed and in a [2 + 2] cycloaddition, 2-methyl-2-propenyl-Af-(2,6-diisopropylphenyl)-imine is generated via an (SiNCO)-ring intermediate.18 36... 

The retrosynthetic analysis of the target molecule 47, which is shown in Scheme 9.16, allows to reduce it to very simple starting materials, such as 2-methyl-2-propene iodide (55) and the chiral A -propionyl-2-oxazolidone 48. The... 

Figure 1 Synthesis of l,4-di[2 -(2 -methyl-2 -propenate)ethyl]phthalate-2,5-dicarboxylic acid (/7-PMDM). 

Ethyl vinyl ether 19a and methyl vinyl ether 19b are metalated by tert-butyllithium at the oxygen-adjacent methine site. -Alkyl groups retard the reaction substantially. Thus, l-methoxy-2-methyl-2-propene was found to be inert toward all... 

Despite the rich chemistry of 45 [18], the only method for accessing this compound is the oxidation of the corresponding alcohol derived from 2-methyl-2-propen-l-ol or other sources, which can be obtained through multi-step operations. In contrast to the known methods, 45 can be readily derived from 44 and 50 by a simple one-pot operation. Since the propargylic alcohol 50 a is readily accessed from a ketone or aldehyde, realization of the transformation of 50 to 45 through a one-pot procedure provides a novel method for carbonyl olefmation of ketones or aldehydes. 

Many examples of the use of chiral Ca-symmetric bis(oxazoline) hgands have been presented here. Other examples include their use in various heteroannulations, one of which is shown in Figure 9.69. Here, the vinyl iodide, (Z)-3-iodo-2-methyl-2-propen-l-ol, 235 is condensed with 1,2-undecadiene to form the 3-methylene-2//-pyran derivative 237. " When this reaction was mn in the presence of 10 mol% of bis(oxazoline) Ugand 236 complexed with palladium(ll), 237 was produced in 70% yield with 79% ee. 

First of all, we have to note the very weak reactivity of allylic ethers in comparison with allylic alcohols (Table l).At a reaction temperature of 60 C, 2,5-dihydrofuran (V) -the most reactive ether among those tested- is about five times less reactive than 2-methyl-2 propen-l-ol (II). 

The prototype for this structural class is 2-methyl-2-propen-l-ol (methallyl alcohol), from which asymmetric epoxidation generates optically active 2-methyloxiranemethanol. Like gly-cidol, 2-methyloxiranemethanol has been difficult to obtain by stoichiometric asymmetric epoxidation, but with the use of the catalytic version, reasonable quantities, are now produced [4] and the compound has become commercially available. In situ derivatization also can be used to recover this epoxy alcohol from the epoxidation reaction. Progress in the isolation of 2-methyloxiranemethanol is reflected in entries 1-3 of Table 6A.3, and the results of in situ derivatization are revealed by entries 4-6. The enantiomeric purity of 2-methyloxiranemethanol produced in this way is very good (92-95% ee), and improvement to 98% ee is observed after recrystallization of the 4-nitrobenzoate derivative. 

C4H oS 75-66-1) see Raloxifene hydrochloride 2-methylpropanoic acid anhydride (C8Hl403 97-72-3) see lbudilast 2-methyl-2-propenal (C4H,0 78-85-3) see Fomepizole 2-mcthyl-2-propcnyl acetate... 

Other volatile compounds found in polystyrene containing packages but of less sensory significance can be 2-methyl-2-propen-l-ol, [3-methylstyrene, trimethyl- and tet-ramethylbenzenes. 

Methyl-2-propen-l-ol 2-Propen-l-ol, 2-methyl- (8,9) (513-42-8) Chlorotrimethylsilane Silane, chiorotrimethyl- (8,9) (75-77-4) 2-(AcetoxymethylJallyltrimethylsilane 2-Propen-l-ol, 2-[(trimethylsilyl)-methyl]-, acetate (10) (72047-94-0)... 

Dianion formation from 2-methyl-2-propen-l-ol seems to be highly dependent on reaction conditions. Silylatlon of the dianion generated using a previously reported method was unsuccessful in our hands. The procedure... 

A 250-mL, three-necked, round-bottomed flask, equipped with a mechanical stirrer and a reflux condenser, is charged with 0.49 g (2.2 mmol) of palladium acetate (Note 1), 20.4 g (100 mmol) of iodobenzene, 9.0 g (125 mmol) of 2-methyl-2-propen-l-ol, 12.6 g (125 mmol) of triethylamine, and 32.5 mL of acetonitrile (Note 2). The reaction vessel is placed in an oil bath at 100°C and the solution is heated to reflux for 11 hr under a nitrogen atmosphere. The reaction mixture is allowed to cool to room temperature and transferred to a 500-mL separatory funnel with the aid of 100 mL of ether and 100 mL of water. The organic layer is washed five times with 100 mL portions of water. The combined aqueous... 

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