32659-21-5Relevant articles and documents
Terpene Cyclizations inside a Supramolecular Catalyst: Leaving-Group-Controlled Product Selectivity and Mechanistic Studies
Zhang, Qi,Catti, Lorenzo,Pleiss, Jürgen,Tiefenbacher, Konrad
supporting information, p. 11482 - 11492 (2017/08/30)
The tail-to-head terpene cyclization is arguably one of the most complex reactions found in nature. The hydrogen-bond-based resorcinarene capsule represents the first man-made enzyme-like catalyst that is capable of catalyzing this reaction. Based on noncovalent interactions between the capsule and the substrate, the product selectivity can be tuned by using different leaving groups. A detailed mechanistic investigation was performed to elucidate the reaction mechanism. For the cyclization of geranyl acetate, it was found that the cleavage of the leaving group is the rate-determining step. Furthermore, the studies revealed that trace amounts of acid are required as cocatalyst. A series of control experiments demonstrate that a synergistic interplay between the supramolecular capsule and the acid traces is required for catalytic activity.
Enantioselective synthesis of allylboronates bearing a tertiary or quaternary B-substituted stereogenic carbon by NHC-Cu-catalyzed substitution reactions
Guzman-Martinez, Aikomari,Hoveyda, Amir H.
supporting information; scheme or table, p. 10634 - 10637 (2010/11/05)
Allylic substitutions that afford α-substituted allylboronates bearing B-substituted tertiary or quaternary carbon stereogenic centers are presented. C-B bond-forming reactions, catalyzed by chiral bidentate Cu-NHC complexes, are performed in the presence of commercially available bis(pinacolato)diboron. Transformations proceed in high yield (up to >98%) and site selectivity (>98% SN2′), and in up to >99:1 enantiomer ratio. Trans- or cis-disubstituted alkenes can be used; alkyl- (linear as well as branched) and aryl-trisubstituted allylic carbonates serve as effective substrates. Allylboronates that bear a quaternary carbon center are air-stable and can be easily purified by silica gel chromatography; in contrast, secondary allylboronates cannot be purified in the same manner and are significantly less stable. Oxidation of the enantiomerically enriched products furnishes secondary or tertiary allylic alcohols, valuable small molecules that cannot be easily obtained in high enantiomeric purity by alternative synthesis or kinetic resolution approaches.
Observations on the direct amidocyclopropanation of alkenes using organozinc carbenoids
Motherwell, William B.,Bégis, Guillaume,Cladingboel, David E.,Jerome, Laure,Sheppard, Tom D.
, p. 6462 - 6476 (2008/02/04)
A series of amidocyclopropanes were prepared by direct amidocyclopropanation of alkenes, using organozinc carbenoids generated from readily available diethoxymethylamides. The amidocyclopropanation of monosubstituted alkenes led to selective formation of the trans-amidocyclopropane in most cases, but with more substituted alkenes, the stereochemical outcome of the cyclopropanation reactions was unpredictable. The amidocyclopropane products can be readily elaborated to structurally interesting cyclopropane containing amino acids or amino alcohols.
