Benzophenone reaction with 2-butene

The 0/7/fo-alkylation of aromatic ketones with olefins can also be achieved by using the rhodium bis-olefin complex [C5Me5Rh(C2H3SiMe3)2] 2, as shown in Equation (9).7 This reaction is applied to a series of olefins (allyltrimethyl-silane, 1-pentene, norbornene, 2,2 -dimethyl-3-butene, cyclopentene, and vinyl ethyl ether) and aromatic ketones (benzophenone, 4,4 -dimethoxybenzophenone, 3,3 -bis(trifluoromethyl)benzophenone, dibenzosuberone, acetophenone, />-chloroacetophenone, and />-(trifluoromethyl)acetophenone). 

The photocycloaddition of a carbonyl compound to an olefin with the formation of an oxetane 3 was first observed by Paterno and Chieffi in 1909.1 They reported obtaining a compound in good yield from the irradiation of benzophenone in a petroleum mixture rich in 2-methyl-2-butene, for which they proposed the oxetane structure. Although Paterno and Chieffi had suggested the correct structure, it was not until 1954 that Buchi and his collaborators reinvestigated this reaction and... 

Table II must apply to both reactions. This has been verified by quenching the photocycloaddition of benzophenone to 2-methyl-2-butene with ferric dipivaloylmethane25 and that of benzaldehyde to cyclohexene with naphthalene.37...

Preparation of 3,5-dimethyl-4-(trifluoromethyl)-2J-heptadien-4-ol. A 1-L, three-necked, round-bottomed flask, equipped with a reflux condenser, a magnetic stir bar and an addition funnel is flame dried under an atmosphere of argon. After the apparatus has cooled, 350 mL of anhydrous diethyl ether (freshly distilled from sodium benzophenone under argon) is added. Lithium wire (6.9 g, 1.0 mol, 3.2-mm diameter, 0.01% Na content, Aldrich Chem. Co., Milwaukee, WI), which is cut into 5- to 10-mm pieces and washed with hexanes, is added to the flask under a counterstream of argon gas. The reaction flask is cooled to 0°C in an ice bath and 68.9 g (0.51 mol) of 2-bromo-cis-2-butene (prepared in the previous step ) in 50 mL of anhydrous diethyl ether is added dropwise over a 45-min period while the reaction mixture is stirred. The reaction solution becomes cloudy due to the formation of lithium bromide. Stirring is continued for an additional 1.5-2 h at 0°C. 

Obtained (trace) by reaction of 2-methyl-3-buten-2-ol with 2,4, 6-tiihydroxy-benzophenone in the presence of boron tfifluoride-etherate in dioxane at 25-30° (<1%) [373]. 

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