41079-58-7Relevant academic research and scientific papers
Synthesis of Cembranoid Analogues through Ring-Closing Metathesis of Terpenoid Precursors: A Challenge Regarding Ring-Size Selectivity
Heidt, Tanja,Baro, Angelika,K?hn, Andreas,Laschat, Sabine
, p. 12396 - 12404 (2015/08/25)
A systematic study on ring-closing metathesis with Grubbs II catalyst to cembranoid macrocycles is described. Acyclic terpenoids with a functional group X in the homoallylic position relative to an RCM active terminus and substituents R, R1 directly attached to the other terminal double bond were prepared from geraniol derived trienes and fragments that are based on bromoalkenes and dimethyl malonate. Such terpenoids were suitable precursors, despite the presence of competing double bonds in their framework. The size of R and R1 is crucial for successful macrocyclization. Whereas small alkyl substituents at the double bond directed the RCM towards six-membered ring formation, cross metathesis leading to dimers dominated for bulkier alkyl groups. A similar result was obtained for precursors without functional group X. In the case of unsymmetrically substituted terpenoid precursor (R=Et, R1=Me) with homoallylic OTBS or OMe group, the RCM could be controlled towards formation of macrocyclic cembranoids, which were isolated with excellent E-selectivity. The role of the substituents was further studied by quantum chemical calculations of simplified model substrates. Based on these results a mechanistic rationale is proposed.
Allylic alkylation and ring-closing metathesis in sequence: A successful cohabitation of Pd and Ru
Kammerer, Claire,Prestat, Guillaume,Gaillard, Thomas,Madec, David,Poli, Giovanni
, p. 405 - 408 (2008/09/19)
An allylic alkylation/ring-closing metathesis domino catalytic process, wherein a palladium and a ruthenium catalyst are concomitantly present in the reaction mixture from the outset of the reaction, is developed. Evidence for Grubbs' catalysts activity in allylic alkylation is also reported.
Ru-catalyzed cyclization of terminal alkynals to cycloalkenes
Varela, Jesus A.,Gonzalez-Rodriguez, Carlos,Rubin, Silvia G.,Castedo, Luis,Saa, Carlos
, p. 9576 - 9577 (2007/10/03)
Cycloalkenes can be efficiently prepared by a new Ru-catalyzed cyclization of terminal alkynals. Under appropriate conditions, cycloisomerizations to conjugated aldehydes may be observed. Both processes involve catalytic Ru vinylidenes. Copyright
Coordinatively unsaturated ruthenium allenylidene complexes: Highly effective, well defined catalysts for the ring-closure metathesis of αω-dienes and dienynes
Fuerstner, Alois,Hill, Anthony F.,Liebl, Monika,Wilton-Ely, James D. E. T.
, p. 601 - 602 (2007/10/03)
The well defined, conveniently accessible and coordinatively unsaturated allenylidene complexes [RuCl2(=C=C=CPh2)(PCy3)2] and [Ru2Cl4(=C=C=CPh2)(PCy3)(n-MeC6/sub
Ligand, Solvent, and Deuterium Isotope Effects in Mn(III)-Based Oxidative Free-Radical Cyclizations
Snider, Barry B.,McCarthy, Bridget A.
, p. 6217 - 6223 (2007/10/02)
Oxidation of β-keto ester 1 with Mn(pic)3 and Cu(OAc)2 affords bicycloalkane 8, not the expected alkene 7, which is formed in high yield with Mn(OAc)3 and Cu(OAc)2.A series of control experiments established that the most likely explanation for this observation is that Mn(pic)2, but not Mn(OAc)2, reacts with the bicyclic radical 5 more rapidly than Cu(OAc)2 does.These studies also indicate the potential for improved yields from oxidative free-radical cyclization of deuterated substrates.For instance, reaction of β-keto ester 1-d with 2 equiv of Mn(OAc)3 and no Cu(OAc)2 affords 65percent of 8, whereas β-keto ester 1 provides only 22percent of 8 under the same conditions.Large kinetic isotope effects change the nature of the termination step and prevent the formation of acyclic radical 3 by intermolecular hydrogen transfer.Solvent and ligand effects on the oxidation of β-keto ester 1, malonate 14, and acetylenic β-keto ester 25 are described.
Cerium (IV) ammonium nitrate promoted oxidative cyclization of dimethyl 4-pentenylmalonate
Baciocchi,Paolobelli,Ruzziconi
, p. 4617 - 4622 (2007/10/02)
CAN promoted oxidative cyclization of dimethyl 4-pentenylmalonate has been investigated in MeOH and in AcOH. The product distribution and the regioselectivity of the reaction (5-exo/6-endo ratio) appear to be very sensitive to the reaction conditions as w
Solvent Effects on Manganese(III)-Based Oxidative Free-Radical Cyclizations: Ethanol and Acetic Acid
Snider, Barry B.,Merritt, John E.,Dombroski, Mark A.,Buckman, Brad O.
, p. 5544 - 5553 (2007/10/02)
Ethanol complements the typical solvent, acetic acid, for Mn(III)-based oxidative free-radical cyclizations.Cyclization of enol ether 1c to give gibberellic acid intermediate 6c is successfull in ethanol, but not in acetic acid.Ethanol acts as a reducing
Cyclizations of unsaturated CR(COX)2 radicals. Manganese(III) acetate oxidative cyclizations of unsaturated acetoacetates and atom-transfer cyclizations of unsaturated haloacetoacetates give the same radicals
Curran, Dennis P.,Morgan, Tina M.,Eric Schwartz,Snider, Barry B.,Dombroski, Mark A.
, p. 6607 - 6617 (2007/10/02)
Comparable regio- and stereochemical results were obtained when cyclizations of a series of 2-substituted 3-oxohept-6-enoate (or oct-7-enoate) esters (acetoacetates) were conducted by manganese(III) acetate oxidation or by iodine or bromine atom transfer
LACTONE FORMATION USING TMSI
Walley, D.R.,Belletire, J.L.
, p. 401 - 406 (2007/10/02)
Iodotrimethylsilane facilitates the rapid lactonization of alcohol ester 2 under remarkably mild conditions.
