Gold-Catalyzed Cyclization of Allene-Substituted Malonate Esters: Synthesis of β,γ-Unsaturated δ-Lactones
摘要:
An efficient method for the preparation of beta,gamma-unsaturated delta-lactones has been developed. The starting materials for the synthesis of these compounds are allene-substituted malonates which undergo gold-catalyzed cyclization by means of nucleophilic attack of the ester moiety on the allene. It is worth mentioning that this is the first example where an ester group attacks as a nucleophile in a gold-catalyzed transformation of allenes.
An Unexpectedly Mild Thermal Alder−Ene-Type Cyclization of Enallenes
作者:Katja Närhi、Johan Franzén、Jan-E. Bäckvall
DOI:10.1021/jo060013g
日期:2006.3.31
A mild, thermal Alder−ene reaction of enallenes has been developed. The allenic double bond acts as the “ene” and generates a carbon−carbon bond to an unactivated olefinic “enophile” in DMF at 120 °C to give [n.3.0] bicyclic systems (n = 3−5) in good yields. Except for a minor [2 + 2] cycloaddition byproduct, the reaction proceeded with complete atom economy, as there is no requirement of a catalyst
已经开发了温和的烯属烃热的Alder-ene反应。烯丙基双键充当“烯”,并在120°C下与未活化的烯烃“亲烯体”产生碳-碳键,从而以高收率得到[ n .3.0]双环体系(n = 3-5)。除了少量的[2 + 2]环加成副产物外,该反应以完全的原子经济性进行,因为不需要催化剂或其他反应物,并且在此过程中不会形成废产物。
Palladium-Catalyzed Oxidative Borylative Carbocyclization of Enallenes
作者:Andreas K. Å. Persson、Tuo Jiang、Magnus T. Johnson、Jan-E. Bäckvall
DOI:10.1002/anie.201008032
日期:2011.6.27
An efficient oxidative carbocyclization/borylation of enallenes uses Pd(OAc)2 as the catalyst, B2pin2 as the boron‐transfer reagent, and 1,4‐benzoquinone (BQ) as the oxidant (see scheme). The reaction seems to take place through activation of the allene by a PdII complex to give an alkenyl–PdII intermediate followed by carbopalladation of the olefin and subsequent cleavage of the intermediate palladium–carbon