A Convergent Synthesis of (�)-?- and ?-Himachalenes
摘要:
Abstract(±)‐α and β‐Himachalene, 5 and 6, have been synthesized in a convergent manner from 3,3‐dimethylacrolein (9), the ester enolate 10 and the silyloxypentadienyllithium 7. The key steps are the regioselective γ‐addition of the dienal 13 to 7 and the intramolecular Diels‐Alder addition 15 → 16. Hydrogenolysis of the diethylphosphate group and functionalization at C (5) completed the synthesis of 5 and 6.
Scope and mechanism of the electrochemical Reformatsky reaction of α-haloesters on a graphite powder cathode in aqueous anolyte
作者:Carlos A. de Souza、Marcelo Navarro、Lothar W. Bieber、Madalena C.C. Areias
DOI:10.1016/j.electacta.2014.03.118
日期:2014.6
carbonyl compounds were submitted to electrochemical coupling on a graphite powder cathode using aqueous anolyte free of organic solvents. Preparative yields of coupling products could be obtained with ethyl 2-bromoisobutyrate and aromatic aldehydes. Ethyl 2-bromopropionate was much less efficient. Extensive variation of applied potential, electrolyte composition, stoichiometry, catalyst, leaving halogen
Reformatsky Reaction in Water: Evidence for a Radical Chain Process
作者:Lothar W. Bieber、Ivani Malvestiti、Elisabeth C. Storch
DOI:10.1021/jo970827k
日期:1997.12.1
The Reformatsky reaction of 2-bromo esters and carbonyl compounds in the presence of zinc can be carried out in concentrated aqueous salt solutions without any cosolvent. The reaction of bromoacetates is greatly enhanced by catalytic amounts of benzoyl peroxide or peracids and gives satisfactory yields with aromatic aldehydes. Preparative yields comparable to those of the traditional procedure are obtained with ethyl 2-bromoisobutyrate. This ester needs no catalyst and reacts even with saturated aldehydes and aromatic ketones, although in law yields. A radical chain mechanism, initiated by electron abstraction from the organometallic Reformatsky reagent, is proposed. Two nonchain pathways, involving radicals directly produced od the metal surface, may compete, especially in the case of secondary and tertiary halides.
Bicyclic Peroxides and Perorthoesters with 1,2,4-Trioxane Structures
作者:Axel G. Griesbeck、Dirk Blunk、Tamer T. El-Idreesy、Angela Raabe