222022-93-7Relevant academic research and scientific papers
Palladium-Catalyzed, tert-Butyllithium-Mediated Dimerization of Aryl Halides and Its Application in the Atropselective Total Synthesis of Mastigophorene A
Buter, Jeffrey,Heijnen, Dorus,Vila, Carlos,Hornillos, Valentín,Otten, Edwin,Giannerini, Massimo,Minnaard, Adriaan J.,Feringa, Ben L.
supporting information, p. 3620 - 3624 (2016/03/23)
A palladium-catalyzed direct synthesis of symmetric biaryl compounds from aryl halides in the presence of tBuLi is described. In situ lithium-halogen exchange generates the corresponding aryl lithium reagent, which undergoes a homocoupling reaction with a second molecule of the aryl halide in the presence of the palladium catalyst (1 mol %). The reaction takes place at room temperature, is fast (1 h), and affords the corresponding biaryl compounds in good to excellent yields. The application of the method is demonstrated in an efficient asymmetric total synthesis of mastigophorene A. The chiral biaryl axis is constructed with an atropselectivity of 9:1 owing to catalyst-induced remote point-to-axial chirality transfer. It takes two: A palladium-catalyzed direct homocoupling of aryl halides in the presence of tBuLi enabled the synthesis of even tetra-ortho-substituted symmetric biaryl compounds in high yield (see scheme). The method was applied to the asymmetric synthesis of mastigophorene A in just eight steps through straightforward enantioselective installation of the benzylic quaternary stereocenter and highly diastereoselective homocoupling.
Enantioselective palladium catalyzed conjugate additions of ortho-substituted arylboronic acids to β,β-disubstituted cyclic enones: Total synthesis of herbertenediol, enokipodin A and enokipodin B
Buter, Jeffrey,Moezelaar, Renee,Minnaard, Adriaan J.
, p. 5883 - 5890 (2014/08/05)
The palladium-catalyzed conjugate addition (Michael addition) of ortho-substituted arylboronic acids to β,β-disubstituted cyclic enones, in particular 3-methyl cyclopent-2-enone and 3-methyl cyclohex-2-enone, is reported. With an achiral bipyridine-based palladium catalyst, good yields are obtained with a variety of ortho-substituted arylboronic acids. In the asymmetric version, good to very high enantiomeric excesses (up to 99% ee) are obtained, though the yields are moderate. The decreased yields are attributed to significant protodeboronation of the arylboronic acid. The developed methodology allows the efficient enantioselective synthesis of the very crowded, biologically active, sesquiterpenes herbertenediol, enokipodin A, and enokipodin B. This journal is the Partner Organisations 2014.
Concise asymmetric synthesis of (-)-herbertenediol
Kita, Yasuyuki,Futamura, Junko,Ohba, Yusuke,Sawama, Yoshinari,Ganesh, Jnaneshuwara K.,Fujioka, Hiromichi
, p. 411 - 413 (2007/10/03)
The rearrangement of the optically active 3-aryl-2-methyl-2,3-epoxy tosylate (>98% ee) afforded the α-keto tosylate with a chiral quaternary carbon center and without loss of chirality. Reductive removal of the tosyloxy group gave the keto compound with a chiral quaternary carbon center, which was converted to (-)-herbertenediol (>98% ee).
The rearrangement of 2,3-epoxysulfonates and its application to natural products syntheses: Formal synthesis of (-)-aphanorphine and total syntheses of (-)-α-herbertenol and (-)-herbertenediol
Kita, Yasuyuki,Futamura, Junko,Ohba, Yusuke,Sawama, Yoshinari,Ganesh, Jnaneshwara K.,Fujioka, Hiromichi
, p. 5917 - 5924 (2007/10/03)
The Lewis acid treatment of 2,3-epoxysulfonates with 2,3-dialkyl substituents or 2-alkyl-3-aryl substituents produced the rearrangement products via C3-cleavage of the oxirane ring in high yields. On the other hand, 2-aryl-3-alkyl-2,3-epoxysulfonates produced the products via C2-cleavage of the oxirane ring. The sulfonyloxy groups of the α-sulfonyloxy ketones, having a chiral benzylic quaternary carbon center obtained by the rearrangement of 2-alkyl-3-aryl-2,3-epoxysulfonates, were reductively eliminated to give the ketones with a chiral benzylic quaternary carbon center. The method was applied to the formal synthesis of (-)-aphanorphine and total syntheses of (-)-α-herbertenol and (-)-herbertenediol.
First total synthesis of the mastigophorenes C and D and of simplified unnatural analogs
Bringmann, Gerhard,Pabst, Thomas,Henschel, Petra,Michel, Manuela
, p. 1269 - 1275 (2007/10/03)
The first total synthesis of the mastigophorenes C (2) and D (3), natural 'dimeric' sesquiterpenes isolated from the liverwort Mastigophora diclados with interesting biological activities, is described. As previously for mastigophorenes A (1) and B, the divergent synthetic approach was first optimized on a simplified model system with a tert-butyl group instead of the chiral cyclopentyl residue, also in order to find more easily available compounds with similar or even improved biological activity.
Nondynamic and dynamic kinetic resolution of lactones with stereogenic centers and axes: Stereoselective total synthesis of herbertenediol and mastigophorenes A and B
Bringmann, Gerhard,Pabst, Thomas,Henschel, Petra,Kraus, Juergen,Peters, Karl,Peters, Eva-Maria,Rycroft, David S.,Connolly, Joseph D.
, p. 9127 - 9133 (2007/10/03)
The stereoselective total synthesis of the sesquiterpene herbertenediol (3) and of its naturally occurring dimers, mastigophorenes A [(P)-1] and B [(M)-1], is described. Following the 'lactone concept', the configuration at the biaryl axis was atropo-dive
Total syntheses of (-)-herbertenediol, (-)-mastigophorene A, and (-)- mastigophorene B. Combined utility of chiral bicyclic lactams and chiral aryl oxazolines
Degnan, Andrew P.,Meyers
, p. 2762 - 2769 (2007/10/03)
A nonracemic bicyclic lactam has been used to construct a chiral cyclopentane containing vicinal quaternary carbon centers in optically pure form, which is common to all of the title compounds. An oxazoline-mediated asymmetric Ullmann coupling was then utilized to establish chirality about the biaryl axis of mastigophorenes A and B. Through the course of this synthesis, it was clearly demonstrated that smaller chiral auxiliaries lead to higher levels of atroposelection, a previously unknown phenomenon of the asymmetric Ullmann coupling.
First synthesis of mastigophorenes A and B, by biomimetic oxidative coupling of herbertenediol
Bringmann, Gerhard,Pabst, Thomas,Rycroft, David S.,Connolly, Joseph D.
, p. 483 - 486 (2007/10/03)
The first synthesis of mastigophorenes A and B by oxidative phenolic coupling of partially protected derivatives of their joint natural monomeric half, herbertenediol, is described. The synthesis starts from this diol itself or from the corresponding aldehyde, both available by isolation from the liverwort, Herbertus aduncus. After transformation of herbertenediol to a chemically appropriate monophenolic coupling precursor, the oxidative dehydrodimerization was brought about using (tert-BuO)2, followed by deprotection to give mastigophorenes A and B in their 'natural' atropisomeric ratio, as isolated from the liverwort.
