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47.1.1.4.1.2 Variation 2: Methylenation of Ketones

DOI: 10.1055/sos-SD-047-00100

Petasis, N. A.Science of Synthesis, (201047168.

The methylenation of ketones with the Tebbe reagent 12 is generally a very efficient process that takes place readily in tetrahydrofuran at 0°C or in the presence of pyridine at lower temperature (Table 3).[‌17‌,‌26‌,‌36‌‌41‌] The procedure generally gives higher yields than methylenation with the corresponding Wittig reagent (Ph3P=CH2), particularly for hindered or readily enolizable ketones.[‌17‌] For example, the methylenation of ketones such as benzophenone or 1-mesitylethanone with the Tebbe reagent (Table 3, entries 1 and 2) gives the alkene products in 97 and 77% yield, respectively, while the corresponding Wittig reaction proceeds with only 46 and 4% yield, respectively.[‌17‌]

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Meeee Meeeeeee Meeeeeee Meeeeeeeee Meeeeee Meeee (%) Mee
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8 Meeee eeeeeee 88, MMM, ee 88 [‌88‌]

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8,8-Meeeeeeeeeeeee (Meeee 8, Meeee 8); Meeeeee Meeeeeeee:[‌88‌]

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(8eM,8eM,8eM)-8,8,8e-Meeeeeeee-8-eeeeeeeeeeeeeeeeee-8M-eeeeeeeeee[e]eeeeeeeee (Meeee 8, Meeee 8); Meeeeee Meeeeeeee:[‌88‌]

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Meeee (8-Meeeeeeeeeeeeeeeeee)eeeeeee (Meeee 8, Meeee 8); Meeeeee Meeeeeeee:[‌88‌]

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References


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