84666-33-1Relevant academic research and scientific papers
Stereoselective Csp3?Csp2 Cross-Couplings of Chiral Secondary Alkylzinc Reagents with Alkenyl and Aryl Halides
Skotnitzki, Juri,Kremsmair, Alexander,Keefer, Daniel,Gong, Ye,de Vivie-Riedle, Regina,Knochel, Paul
, p. 320 - 324 (2020)
We report palladium-catalyzed cross-coupling reactions of chiral secondary non-stabilized dialkylzinc reagents, prepared from readily available chiral secondary alkyl iodides, with alkenyl and aryl halides. This method provides α-chiral alkenes and arenes with very high retention of configuration (dr up to 98:2) and satisfactory overall yields (up to 76 % for 3 reaction steps). The configurational stability of these chiral non-stabilized dialkylzinc reagents was determined and exceeded several hours at 25 °C. DFT calculations were performed to rationalize the stereoretention during the catalytic cycle. Furthermore, the cross-coupling reaction was applied in an efficient total synthesis of the sesquiterpenes (S)- and (R)-curcumene with control of the absolute stereochemistry.
Synthesis of cyclic alkenylsiloxanes by semihydrogenation: A stereospecific route to (Z)-alkenyl polyenes
Elbert, Bryony L.,Lim, Diane S. W.,Gudmundsson, Haraldur G.,O'Hanlon, Jack A.,Anderson, Edward A.
supporting information, p. 8594 - 8598 (2014/07/21)
Cyclic alkenylsiloxanes were synthesized by semihydrogenation of alkynylsilanes - a reaction previously plagued by poor stereoselectivity. The silanes, which can be synthesized on multigram scale, undergo Hiyama-Denmark coupling to give (Z)-alkenyl polyene motifs found in bioactive natural products. The ring size of the silane is crucial: five-membered cyclic siloxanes also couple under fluoride-free conditions, whilst their six-membered homologues do not, enabling orthogonality within this structural motif.
Enantioselective total synthesis and confirmation of the absolute and relative stereochemistry of streptorubin B
Hu, Dennis X.,Clift, Michael D.,Lazarski, Kiel E.,Thomson, Regan J.
supporting information; experimental part, p. 1799 - 1804 (2011/04/15)
The enantioselective total synthesis of the pyrrolophane natural product streptorubin B is described. Key steps in the concise route include the application of a one-pot enantioselective aldol cyclization/Wittig reaction and an anionic oxy-Cope rearrangement to forge the crucial 10-membered ring. Comparisons between CD spectra of synthetic and natural samples of streptorubin B coupled with X-ray crystallography allowed for the determination of the absolute stereochemistry of this natural product for the first time. These studies also provided unambiguous proof of the relative configuration between the butyl side chain and the bispyrrole subunit. Additional studies revealed a novel atropstereoselective Paal-Knorr pyrrole condensation and provided fundamental experimental insight into the barrier for atropisomerization of the natural product.
Glycosidase inhibitors: Synthesis of enantiomerically pure aza-sugars from Schiff base amino esters via tandem reduction-alkenylation and osmylation
Polt, Robin,Sames, Dalibor,Chruma, Jason
, p. 6147 - 6158 (2007/10/03)
Nitrogen-in-the-ring 'aza-sugars' have been synthesized in enantiomerically pure form from the amino acid L-alanine in excellent overall yield. The O'Donnell's Schiff base of L-alanine methyl ester 9a was converted to aza-sugar L-fuco-1-deoxy-nojirimycin, 18, and to the epimer L-gulo-1- deoxy-nojirimycin, 20, in eight steps. The overall yields were 20 and 29%, respectively. The methodology for the efficient generation of silyl- and benzyl-protected (E)-3-lithio-2-propen-1-ols, and the use of these alkenyllithiums with iBu5Al2H as nucleophiles in the threo-selective tandem reduction-alkenylation of the Schiff base esters is described. Osmium- catalyzed cis-oxygenation of the resulting olefin products was selective for the galacto (fuco) amino polyols in all cases for the acyclic olefins, and was gulo-selective for the cyclic D-4,5-dihydropyridine pivalate, 17c. TEMPO- NaOCl was selective for oxidation of the primary position of the acyclic Schiff bases, and allowed for minimal protection/deprotection of the intermediates. The resulting N-benzhydryl heterocycles were easily deprotected with H2-Pd at atmospheric pressure.
A route to the pyrrolo[1,2-a]indolenine ring system via intermolecular organolithium addition to an oxindole
Jones,Storey
, p. 4901 - 4906 (2007/10/02)
A synthesis of the pyrrolo[1,2 a]indolenine 6 in four steps from N-benzyl-3,3-dimethyloxindole 2 is presented involving an organolithium addition to the oxindole carbonyl group. Additions of vinyllithiums to the oxindole 2 are presented.
PREPARATION OF IODOALLYLIC ALCOHOLS VIA HYDROSTANNYLATION: SPECTROSCOPIC PROOF OF STRUCTURES
Jung, Michael E.,Light, Lynn A.
, p. 3851 - 3854 (2007/10/02)
Hydrostannylation of propargylic alcohols and ethers affords either the E- or Z-β-tributylstannylallylic alcohols and ethers as the major products by the use of excess stannane or acetylenic compound, respectively; europium shift studies in the high field
