Trimethyl-1 -phenyl-1 -butanone

HEXAHYDRO-4, 4,7-TRIMETHYL-4H-l,3-BEN20XATHIXN 4H-1, 3-BENZOXATHIIN, HEXAHYDRO-4,4, 7-TRIMETHYL- (59324-06-0), 65, 215 Hydrazine, (1,1-diraethylethyl)-, monohydrochloride, 65, 166 Hydrazine, tert-butyl, monohydrochloride, 65, 166 Hydrogen peroxide (7722-84-1), 65, 166 3-HYDR0XY-3-METHYL-1-PHENYL-1-BUTAN0NE 1-BUTANONE,... 

Olefin synthesis. This reagent has an advantage over trialkyl phosphites (see Trimethyl phosphite, 1, 1233, and this volume) for stereospecific generation of olefins from trithio- and thionocarbonates in that the conditions are mild (30°)-s Thus optically active /rans-cyclooctene (6) has been prepared from cis-cyclooctene in the following way.3 Addition of thiocyanogen to cis-cyclooctene (3) affords trans-, 2-dithiocyanocyclooctane (4), which when refluxed with 47% hydrobromic acid affords the iminodithiocarbonate (5). This was resolved via the salt with (—)-l-phenyl-ethanesulfonic acid by thirteen recrystallizations from 2-butanone. The (+)-(5) was... 

An autoclave charged with 3-hydroxy-3-methyl-2-butanone, benzaldehyde, GaCla, and NH4GI, anhydrous NHg introduced with stirring until a pressure of 80 p.s.i.g. is obtained, then heated 4 hrs. at 90-100°/300-400 p.s.i.g. 2-phenyl-4,5,5-trimethyl-3-oxazoline. Y 96%. F. e. s. J. R. Gaines and G. R. Hansen, J. Heterocyclic Ghem. 96 (1964). 

Discuss the role of the Lewis acid and the solvent polarity in the control of the di-astereoselectivity of the reaction. Considering the previous discussion, predict the stereochemistry of the product/s obtained in the reduction of 2,3,3-trimethyl-l-phenyl-l-butanone under the same conditions employedfor compound 1. 

The 2,3,3-trimethyl-l-phenyl-l-butanone is an a-substituted ketone, but the a-substituents have no ability to chelate metals. In that case, the role of the Lewis acid will be just to coordinate the oxygen atom, enhancing its reactivity towards the nucleophilic attack. The same open FeUdn-Ahn s model previously commented will be valid for both, TiCU and CeCls-mediated reductions, as it is shown in Scheme 4.4. Again, the first step of the reaction is the coordination of the Lewis acid with the carbonyl group. Although a priori, conformations 9 and 10 could be considered, hydride attack to the carbonyl group in 9 should be favored by steric effects leading to the ti-alcohol 11 as the main reaction product in both cases. 

---