close

Вход

Забыли?

вход по аккаунту

?

код для вставки
2005
Pyran derivatives
R 0340
Stereoselective Synthesis of Tetrahydropyran-4-ones from Dioxinones Catalyzed
Scandium(III) Triflate. — β-Hydroxy-dioxinones and aldehydes undergo mild
33- 141 by
and stereoselective cyclizations in the presence of catalytic amounts of scandium
triflate. Saturated aldehydes participate in the cyclization, with linear systems being
superior to α-branched substrates in terms of yield. The overall diastereoselectivity of
the reaction is dependent on the structure of the aldehyde. (IVc), (IVf) and (IVg) provide reduced levels of selectivity compared to unbranched saturated or electron-deficient substrates. The direct addition of a range of alkoxide nucleophiles to the reaction
flask converts the novel resulting bicyclic pyrans into carboxy-substituted tetrahydropyran-4-ones as a keto-enol mixture, thereby accessing a highly efficient three-component process. (IIIc), when exposed to heat, generates a reactive acylketene, which is
trapped to give (XV) or (XVII). — (MORRIS, W. J.; CUSTAR, D. W.; SCHEIDT*, K.
A.; Org. Lett. 7 (2005) 6, 1113-1116; Dep. Chem., Northwest. Univ., Evanston,
IL 60208, USA; Eng.) — R. Steudel
2005
Документ
Категория
Без категории
Просмотров
0
Размер файла
44 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа