Surface-Mediated Reactions. 6. Effects of Silica Gel and Alumina on Acid-Catalyzed Reactions
摘要:
Adsorption of a variety of acids to chromatographic silica gel results in substantial enhancement of their catalytic activity-affording easily prepared, environmentally benign heterogeneous acids that are highly effective in mediating a number of processes. This was shown for the isomerization of allene 1 and dimerization of the corresponding 1,3-diene 2; cyclization of (R)-citronellal (5), the related diester 10, and 1,5-cyclooctadiene (15); Rupe rearrangement of alkynol 18; and Friedel-Crafts cyclodehydration of alcohols 21. By contrast, commercially available Nafion-H was significantly less effective as a heterogeneous acid catalyst. Chromatographic alumina displayed enigmatic behavior, showing enhanced acidity on the adsorption of HCl but little or no acidity on the adsorption of a variety of other types of acid. The results are discussed in terms of the surface structures of silica gel and alumina.
Enecarboxylation with diethyl oxomalonate as an enophilic equivalent of carbon dioxide. A synthesis of allylcarboxylic acids
作者:Mary F. Salomon、Simon N. Pardo、Robert G. Salomon
DOI:10.1021/ja00325a014
日期:1984.6
On prepare une serie d'acides carboxyliques allyliques a partir des olefines correspondantes par un processus en deux etapes equivalent a: 1) une reaction ene avec l'oxomalonate de diethyle conduisant a l'ester α-hydroxymalonique; 2) une bisdecarboxylation oxydante de ce dernier
在制备 une serie d'acides carboxyliques allyliques a partir des ocoxyliques par un processus en deux etapes 等价物 a: 1) une 反应 ene avec l'oxomalonate de diethyle conduisant a l'ester α-hydroxymalonique; 2) une bisdecarboxylation oxydante de ce dernier
Generation of ester enolates by reductive a-deacetoxylation
作者:Simon N. Pardo、Subrata Ghosh、Robert G. Salomon
DOI:10.1016/s0040-4039(01)90468-x
日期:1981.1
Diethyl allylmalonates or 2-arylalkanoic esters are prepared in good yield by reductive α-deoxygenation of the corresponding α-acetoxy or α-alkony esters. Since the intermediate ester enolates are generated under aprotic conditions, a one pot reductive-alkylation is also possible. One application of this procedure allows diethyloxomalonate to serve as a conjunctive reagent for stitching together an
Functionalization of saturated hydrocarbons. High temperature bromination of octahydropentalene. Part 19
作者:Duygu D. Günbaş、Fatih Algı、Tuncer Hökelek、William H. Watson、Metin Balci
DOI:10.1016/j.tet.2005.09.019
日期:2005.11
The synthesis and thermal bromination of octahydropentalene was studied. The reaction afforded 1a,3a,4b,6b-tetrabromo-1,2,3,4,5,6-hexahydropentalene (14) with remarkable regio- and stereospecificity. The structure of the product was determined by 1H and 13C NMR data and single X-ray structural analysis. The treatment of octahydropentalene with tenfold bromine gave the octabromopentalene derivative
研究了八氢戊烯的合成和热溴化反应。反应得到具有显着的区域和立体特异性的1a,3a,4b,6b-四溴-1,2,3,4,5,6-六氢戊烯(14)。产物的结构通过1 H和13 C NMR数据以及单X射线结构分析确定。用十倍溴处理八氢戊烯得到八溴戊二烯衍生物。讨论了产品的形成机理。
Atom transfer addition and annulation reactions of propargyl iodomalononitrile
作者:Dennis P. Curran、Churl Min Seong
DOI:10.1016/s0040-4020(01)88881-5
日期:1992.1
Heating of propargyl iodomalonitrile with mono-, di- or trisubstituted alkenes followed by reduction of the crude or isolated products with tributyltin hydride produces dicyano(methylene)cyclopentanes in good to excellent overall yield. This radical annulation is often highly regio and stereoselective. The mechanism is discussed.
applications in organic synthesis, metal catalysis, and organocatalysis. Their potential as ligands for first‐row transition‐metal catalysts inspired a new method to access complex poly‐heterocyclic pyrrolidines in one step from available materials. This fundamental step forward is based on the discovery of an essential organoaluminum promoter that engages unactivated and electron‐rich olefins in intermolecular