2.2.4.4- Tetramethyl-3-pentanone

Dehydration of 2 2 3 4 4 pentamethyl 3 pentanol gave two alkenes A and B Ozonolysis of the lower boiling alkene A gave formaldehyde (H2C=0) and 2 2 4 4 tetramethyl 3 pentanone Ozonolysis of B gave formaldehyde and 3 3 4 4 tetramethyl 2 pentanone Identify A and B and suggest an explanation for the formation of B in the dehydration reaction... 

Monobasic solutes that have no carbinyl hydrogens may also show nonequivalence. 3-Methyl-2-butanone, 4-methyl-2-pentanone, 2-methylpropanal, methyl 2-methylbutyrate, 2,2,6,6-tetramethyl-piperidine, methyldiisopropylcarbinol, and methylethyl-n-butyl-carbinol in TFAE-saturated benzene all show nonequivalence of sufficient magnitude (0.01-0,03 ppm) to allow nonequivalence sense determination at 220 MHz. An especially striking example is that provided by pyrazolines 26. With only a severalfold excess of (S)-TFAE, 3(5),5(S)-enriched samples of these compounds show nonequivalence in their methyl resonances (downfield sense for the singlets and upfield sense for the triplets) sufficient for enantiomeric purity determination at 90 MHz (52). 

Hydrocarbonylation of 1,4-dienes.3 Hydrocarbonylation of 1,4-pentadiene catalyzed by Co2(CO)8 results in 2-methylcyclopentanone as the only cyclic product. As expected, a gem-dimethyl group at C3 enhances the tendency to form cyclo-pentanones. Thus hydrocarbonylation of the 1,4-diene 1 leads to the tetramethyl-cyclopentanone 2 with a marked preference for the cw-isomer. The reaction has... 

In exploring various synthetic methods for the preparation of 1,2-oxaphospholene 2-oxides we investigated the reaction of diacetone alcohol (4-hydroxy-4-methyl-2-pentanone) with methyl and phenylphosphonous dichloride, which was reported (1) to proceed as shown in eq (1) to give 2,3,3,5-tetramethyl-l,2-oxaphos-phol-4-ene 2-oxide or the corresponding 2-phenyl derivative. 

Tetramethyl-l,3-cyclobutanedione, dimethylketene dimer (12), was hydrogenated to the corresponding glycol in excellent yields with Ru-C as catalyst in methanol at 125°C and 6.9-10.3 MPaH2 (eq. 5.41).131 Hydrogenation over Raney Ni in methanol was often accompanied by formation of a high-boiling byproduct that was shown to consist of 1-hydroxy-2,2,4-trimethyl-3-pentanone (13) and methyl 2,2,4-trimethyl-3-oxovalerate (14). 

Tetramethyl-3-piperideine (35) may be prepared from mesityl oxide via diacetoneamine (4-amino-4-methyl-2-pentanone) and reaction with acetaldehyde to give 2,2,6-trimethyl-4-piperidone, which is then treated with methylmagnesium iodide and dehydrated.28... 

Primary amines form Schiff bases, (CH )2C=NR. Ammonia induces an aldol condensation followed by 1,4-addition of ammonia to produce diacetone amine (from mesityl oxide), 4-amino-4-methyl-2-pentanone [625-04-7], (CH3)2C(NH2)CH2COCH3, and triacetone amine (from phorone), 2,2,6,6-tetramethyl-4-piperidinone [826-36-8]. Hydroxylamine forms the oxime and hydrazine compounds (RNHNHJ form hydrazones (RNHN=C(CH3)2). Acetone and nitrous acid give the isonitroso compound which is the monoxime of pymvaldehyde [306-44-5], CH COCH=NOH. 

Non-enolizable aliphatic ketones are cleaved analogously. For example, pivalamide and isobutane are formed in good yield from hexamethylacetone (2,2,4,4-tetramethyl-3-pentanone). Most unsymmetrically substituted ketones afford the four possible products (2 amides and 2 hydrocarbons), but often in unequal amounts, e.g., pivalamide and 2,2-diethylbutyramide in 5 1 proportions from 4,4-diethyl-2,2-dimethyl-3-hexanone. Hexaalkyl-substituted acetone derivatives containing branched alkyl groups generally do not react. 

Tetrahydro-2,3,5,6-tetramethyl-y-pyrone (1). A 12-L, three-necked, round-bottomed flask fitted with an efficient mechanical stirrer and a gas inlet is flushed with dinitrogen. Under a dinitrogen flush, 2360 mL of methanol and 380 g (6.77 mol) of KOH are added to the flask. The solution is then cooled to 0°C in an ice bath and 2000 mL (18.9 mol) 3-pentanone (Aldrich) is added under a dinitrogen flush. The solution is maintained at 0°C, and 4245 mL (75.5 mol) of acetaldehyde (Fluka, puriss) is added dropwise with stirring over a period of 36 h. During the addition of acetaldehyde, the color of the reaction mixture changes to a deep red, then to a dark brownish red color. After acetaldehyde addition is complete, the reaction solution is stirred an additional 12h at 0°C. 

Benzophenone would be 1,1-diphenylmethanone, but because it is derivative of benzene, benzophenone is taken as the lUPAC name (see Chapter 21, Section 21.2). Pinacolone is 2,2,4,4-tetramethyl-3-pentanone. 

It is known that the reaction of ethylmagnesium bromide with 2,2,4,4-tetramethyl-3-pentanone does not give the expected alcohol product. In fact, the ketone is reduced to an alcohol and ethylmagnesium bromide is converted to ethene. Reductions are discussed in Chapter 19, but offer a reason for the fact that this ketone does not undergo normal acyl addition. 

Aldehydes and ketones of wide variety such as caproaldehyde, benzaldehyde, 2-heptanone, and norcamphor utilize 1 equiv of hydride in THF and are reduced rapidly and quantitatively to the corresponding alcohols at 15 2 °C. The hindered ketone, 2,2,4,4-tetramethyl-3-pentanone, which is inert to 9-BBN [5], however, is rapidly reduced with Li9-BBNH. Reduction of camphor gives 91% isoborneol and 9% borneol (Eq. 25.13). 

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