Geminal selectivity

Geminal selectivity with respect to a bulky vinyl substituent. 849... 

TABLE 7. Geminal selectivity in the photooxygenation of alkenes 45-48 bearing an aUyUc functionality ... 

SCHEME 16. Mechanism of the geminal selectivity in the photooxygenation of alkenes bearing a large alkyl substituent in allylic position... 

Geminal selectivity is also observed in cases where the bulky substituent is in a vinylic position . Examples with compounds 60-65 are shown in Table 10. 

On the basis of similar arguments, previously proposed, transition state TSi is expected to have lower energy than TS2 (Scheme 18) and thus account for the geminal selectivity of alkenes with the large L group in the vinyl position. 

Michael Orfanopoulos, Georgios C. Vougioukalakis and ManoUs Stratakis TABLE 10. Geminal select vity with respect to a bulky vinyl substituent in 60-65 ... 

For alkenes bearing an electron-withdrawing group at the a-position such as aldehyde, carboxylic acid, ester, ketone , imine , sulphoxide and cyano °, a high degree of geminal selectivity has been demonstrated. The results are summarized in Table 13. 

Table 5 Geminal Selectivity in the Photo-Oxygenation of Alkenes Bearing an Allylic Functionality3...

An alternative explanation of the geminal selectivity was based on a previous computational model proposed by Houk et al. [61], According to this model, the lower the calculated rotational barrier, the higher the reactivity of the alkyl group. 

C. Geminal Selectivity With Respect to a Bulky Vinyl Substituent... 

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