29949-93-7Relevant academic research and scientific papers
Tandem radical nitrile transfer-cyclization reactions of 1,3- dioxane-4-nitriles: Synthesis of spirocyclic systems
Rychnovsky, Scott D.,Swenson, Sonja S.
, p. 16489 - 16502 (1997)
Reduction of remote halogen substituents with n-Bu3SnH leads to efficient 1,4- and 1,5-nitrile transfer from 1,3-dioxane-4-nitriles and subsequent stereoselective reduction. These radical-transfer reactions provide a mild alternative to the Li/
Suzuki-Miyaura Coupling Reactions of Conjunctive Reagents: 2-Borylated Allylic Sulfones
Altenhofer, Erich F.,Harmata, Michael
, p. 8168 - 8174 (2015/09/01)
In support of various efforts in our group, we developed methods for the convenient Suzuki-Miyaura coupling of borylated allylic sulfones with various electrophiles in both inter- and the less common intramolecular modes. The procedure facilitates the preparation of a wide variety of sulfones in a straightforward fashion, including six- through eight-membered rings.
Rhodium-catalyzed vinylcyclopropanation/cyelopentenation of strained alkenes via a sequential carborhodation process
Tseng, Nai-Wen,Lautens, Mark
supporting information; experimental part, p. 2521 - 2526 (2009/08/07)
A rhodium-catalyzed reaction of dienylboronate esters with alkenes is described. Strained bicyclic alkenes show the highest reactivity toward the rhodium-catalyzed addition of the dienylboronate esters. Depending on the substitution pattern of dienylboron
Total synthesis of (-)-histrionicotoxin 285A and (-)- perhydrohistrionicotoxin
Macdonald, James M.,Horsley, Helen T.,Ryan, John H.,Saubern, Simon,Holmes, Andrew B.
supporting information; experimental part, p. 4227 - 4229 (2009/06/06)
(Chemical Equation Presented) Starting from commercially available (S)-glycidol, and via a common intermediate, the total synthesis of (-)-histrionicotoxin 285A and (-)-perhydrohistrionicotoxin has been achieved. Key to this synthesis was the efficient co
EPOTHILONE DERIVATIVES
-
Page/Page column 19-20; 45-46, (2010/02/14)
Epothilone derivatives of Formula (I) and their use as a pharmaceutical.
Stereochemical models for the enantiocontrolled construction of fully functionalized C rings via intramolecular aldolization in advanced precursors to paclitaxel
Paquette, Leo A.,Zeng, Qingbei,Tsui, Hon-Chung,Johnston, Jeffrey N.
, p. 8491 - 8509 (2007/10/03)
Six transition-state models for intramolecular aldol C-ring annulation in suitably substituted bicyclo-[6.2.1]undecanones have been defined. The first consideration is the inherent conformational flexibility of the nine- membered ketonic ring which does not limit effective deprotonation to a single C-8 epimer. When the oxygen substituents at C-4 and C-5 are not covalently linked, the configuration at C-5 defines the stereochemical course of the ring closure, with only the β series being amenable to the proper elaboration of paclitaxel. When C-4 and C-5 are incorporated into a 1,3- dioxane ring instead, the principal stereocontrol element is translocated into the aryl-substituted carbon of the cyclic acetal. To the extent that the Ar group remains equatorially disposed, then proper aldolization will materialize in only one of the four possible diastereomers. Experimental tests that are provided for three of the models are shown to conform to expectations. This analysis of the origin of stereoselectivity has, for the first time, defined the scope and limitations associated with C-ring closure by means of the aldol protocol.
Total Synthesis of Epothilones A and B
Dongfang, Meng,Bertinato, Peter,Balog, Aaron,Su, Dai-Shi,Kamenecka, Ted,et al.
, p. 10073 - 10092 (2007/10/03)
Convergent, stereocontrolled total syntheses of the microtubule-stabilizing macrolides epothilones A (2) and B (3) have been achieved. Four distinct ring-forming strategies were pursued (see Scheme 1). Of these four, three were reduced to practice. In one approach, the action of a base on a substance possessing an acetate ester and a nonenolazable aldehyde brought about a remarkably effective macroaldolization see (89 -> 90 + 91; 99 -> 100 + 101), simultaneously creating the C2-C3 bond and the hydroxyl-bearing stereocenter at C-3. Alternatively, the 16-membered macrolide of the epothilones could be fashioned through a C12-C13 ring-closing olefin metathesis (e.g. see 111 -> 90 + 117; 122 -> 105 + 123) and through macrolactonization of the appropriate hydroxy acid (e.g. see 88 -> 93). The application of a stereospecific B-alkyl Suzuki coupling strategy permitted the establishment of a cis-C12-C13 olefin, thus setting the stage for an eventual site- and diastereoselective epoxidation reaction (see 96 -> 2; 106 -> 3). The development of a novel cyclopropane solvolysis strategy for incorporating the geminal methyl groups of the epothilones (see 39 -> 40 -> 41), and the use of Lewis acid catalyzed diene-aldehyde cyclocondensation (LACDAC) (see 35 + 36 -> 37) and asymmetric allylation (see 10 -> 76) methodology are also noteworthy.
Free-Radical Homolytic Substitution at Selenium: An Efficient Method for the Preparation of Selenophenes
Lyons, Jennifer E.,Schiesser, Carl H.,Sutej, Katarina
, p. 5632 - 5638 (2007/10/02)
Substituted and unsubstituted 1-(benzylseleno)-4-iodobut-3-en-2-ols 12 and 2-(benzylseleno)-1-(2-iodophenyl)ethanols 18 react smoothly with tris(trimethylsilyl)silane in benzene at 80 deg C (AIBN initiator) to afford selenophenes 16 and benzoselenophenes 21 in excellent yield.These reactions presumably involve intramolecular homolytic substitution by aryl and vinyl radicals 14 and 20 at the selenium atom with the expulsion of benzyl radical followed by facile dehydration to afford the aromatic selenophene ring system in each case.Competitive rate studies on the ring closure of the 2-phenyl radical 25 in the presence of tri-n-butyltin hydride to give 2,3-dihydrobenzoselenophene (27) and 1-(benzylseleno)-2-phenylethane (28) provide a rate constant for ring closure (kc) of approximately 3E7 s- at 80 deg C.The determination of more accurate data is hampered by what we attribute to be the involvement of a slow, but competive nonradical process.
Z-1-VINYLIODIDE DURCH WITTIG-REAKTION
Bestmann, Hans Juergen,Rippel, Hans Christoph,Dostalek, Roman
, p. 5261 - 5262 (2007/10/02)
A wide spectrum of Z-1-iodo-alkenes is available by Wittig reaction of iodomethylenetrimethylphosphorane with aldehydes.The formation of 1,1-diiodo-1-alkenes as byproducts is explained.
