Delineation of the factors governing reactivity and selectivity in epoxide formation from ammonium ylides and aldehydes.
نویسندگان
چکیده
Diastereoselectivity in reactions of aryl-stabilised ammonium ylides are highly sensitive to the nature of the amine and the ylide substituent. DFT calculations are consistent with a mechanism in which reversibility in betaine formation [despite the high energy (and therefore instability) of ammonium ylides] is finely balanced due to the high barrier to ring closure.
منابع مشابه
Identification of the best-suited leaving group for the diastereoselective synthesis of glycidic amides from stabilised ammonium ylides and aldehydes.
In comparison to the use of sulfur ylides, the use of ammonium ylides for the synthesis of epoxides is significantly less developed. As a part of our systematic investigations concerning the use of amide-stabilised ammonium ylides for the synthesis of glycidic amides we have focused on the identification of the best-suited amino leaving group for this purpose. Whereas tertiary amines like quinu...
متن کاملAmmonium ylides for the diastereoselective synthesis of glycidic amidesw
The (dia-)stereoselective synthesis of glycidic amides and esters has attracted considerable interest over the last few decades mainly due to the high potential of these compounds as synthetically useful intermediates in a variety of organic syntheses. Ylides have proven to be very powerful synthons for the formation of epoxides providing alternatives to the oxidation of a,b-unsaturated carbony...
متن کاملAmmonium ylides for the diastereoselective synthesis of glycidic amides.
A highly trans-selective protocol for the synthesis of glycidic amides was developed. This approach gave access to oxiranes by reacting stabilised ammonium ylides bearing an α-carbonyl group and aromatic aldehydes in moderate to good yields.
متن کاملThe complexity of catalysis: origins of enantio- and diastereocontrol in sulfur ylide mediated epoxidation reactions.
The reaction of chiral sulfur ylides with aldehydes and ketones has emerged as a useful asymmetric process for the synthesis of epoxides. Processes employing either catalytic or stoichiometric amounts of sulfides have been developed. Although a large number of chiral sulfur ylides have been tested in the epoxidation process, only a few have delivered high diastereo- and enantio- selectivity. Th...
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Preparation of 2-Chlorobenzonitrile, and benzonitrile are reported here from the corresponding 2-Chlorobenzaldehyde and benzaldehyde by the reaction of ammonium hydroxide/VPO titania, VPO bulk (...
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ورودعنوان ژورنال:
- Organic & biomolecular chemistry
دوره 4 4 شماره
صفحات -
تاریخ انتشار 2006