Krische allylation

The remainder of the right-hand fragment was prepared (Scheme 5) in accord with our efforts in the theopederin D synthesis. Keto-aldehyde 21, available through the condensation of the enamine of isobutyraldehyde with acetyl chloride, was subjected to a Krische allylation to provide secondary alcohol 22 in 93% ee. Protection as a triethylsilyl ether and exposure to TMSOTf yielded enolsilane 23. The enolsilane was selected as the nucleo-phile for the fragment-coupling aldol reaction based on Evans studies on the influence of various substituents on complex aldol reactions. While the silyloxy group in aldehyde 20 was expected to direct nucleophiles toward the undesired face of the aldehyde, consistent with the extended Felkin model,the methyl group adjacent to the aldehyde was expected to direct the nucleophile to the desired face of the aldehyde, in accord with the... 

Furthermore, following an analogous methodology, combining the Morita-Baylis-Hillman reaction and the Trost-Tsuji reaction, Krische and co-workers have obtained allyl-substituted cyclopentenones 94 [84], Reaction was initiated by Michael addition of tributyl phosphine to an enone moiety 92, generating a latent enolate 93 which reacts intramolecularly with a jr-allylPd complex as the electrophile partner. A final -elimination step of trib-utylphosphine, favored by the presence of the methoxide ion, delivered the substituted cyclopentenones 94 (Scheme 36). 

Af-anion through the benzenoid system. The Krische group has also reported the iridium-catalyzed enantioselective allylation, crotylation, or prenylation of isatins [46],... 

Krische and co-workers have investigated the tertiary phosphine-catalyzed regjospecific allylic amination of MBH acetates through a tandem 5n2 -5n2 mechanism by using phthalimide derivatives as nucleophiles. When (1 )-C1-MeO-BIPHEP was used as a catalyst, the MBH adduct obtained from p-nitrobenzaldehyde and methyl acrylate reacted with phthalimide to give the allylic substituted product 297 in 80% yield with 56% ee (Scheme 3.126). ... 

Organophosphine-catalyzed allylic amination of MBH adducts has also been applied for the synthesis of a-alkylidene-(3-amino carbonyl compounds. The first catalytic asymmetric example of this reaction was reported by Krische and coworkers [122] in 2004 (Scheme 11.41), who showed the addition of phthalimide to MBH acetate in the presence of 20mol% of commercially available chiral phosphine catalyst (7 )-Cl-MeO-BlPHEP 54. The reaction was carried out at 50°C however, a long reaction time (62 h) was required. The substitution product was produced in 80% isolated chemical yield and with only 56% of... 

Han SB, Kim IS, Krische Ml (2009) Enantioselective iridium-catalyzed carbonyl allylation from the alcohol oxidation level via transfer hydrogenation minimizing pre-activation for synthetic efficiency. Chem Commun 7278-7287... 

Patman RL, Bower JF, Kim IS, Krische MJ (2008) Formation of C-C bonds via catalytic hydrogenation and transfer hydrogenation vinylation, allylation, and enolate addition. Aldrichim Acta 41 95-104... 

Kim IS, Ngai M-Y, Krische MJ (2008) Enantioselective iridirrm-catalyzed carbonyl allylation from the alcohol or aldehyde oxidatimr level using allyl acetate as an allyl metal sirrrogate. J Am Chem Soc 130 6340-6341... 

Lu Y, Kim IS, Hassan A, Del Valle DJ, Krische MJ (2009) 1, n-Glycols as dialdehyde equivalents in iridium-catalyzed enantioselective carbonyl allylation and iterative two-directional assembly of 1,3-polyols. Angew Chem Int Ed 48 5018-5021... 

Hassan A, Lu Y, Krische MJ (2009) Elongation of 1,3-polyols via iterative catalyst-directed carbonyl allylation from the alcohol oxidation level. Org Lett 11 3112—3115... 

Schmitt DC, Dechert-Schmitt A-MR, Krische MJ (2012) Iridium-catalyzed allylation of chiral P-stereogenic alcohols bypassing discrete formation of epimerizable aldehydes. Org Lett 14 6302-6305... 

Shin I, Wang G, Krische MJ (2014) Catalyst-directed diastereo- and site-selectivity in successive nucleophilic and electrophilic allylations of chiral 1,3-diols protecting-group-lree synthesis of substituted pyrans. Chem Eur J 20 13382-13389... 

In 2004, Krische and colleagues demonstrated that exposure of Morita-Baylis-Hillman acetates to tertiary phosphine catalysts in the presence of 4,5-dichlorophthalimide enabled regiospecific allylic substitution through a tandem Sn2 -Sn2 mechanism. Through the use of the chiral phosphine catalyst, (i )-Cl-MeO-BIPHEP, the racemic Morita-Baylis-Hillman acetate depicted in Scheme 2.108 was converted into the corresponding enantiomerically enriched allylic amination product, thus establishing the feasibility of DKR. 

Ir -aUyl complexes can also act as nucleophiles in additing to various electrophiles such as aldehydes, ketones, or imines. Krische et al. [143d] have developed a broad new family of enantioselective allylations via hydrogenations and transfer... 

Krische et al. used Ru catalysts for the addition of allyl equivalents such as ahenamides or conjugated dienes to alcohols or carbonyl compounds. The exposure of alcohols 214 to ahenamides 215 in the presence of RuHCl(CO)(PPh3)3 and the ligand dippf (bis(diisopropylphosphino)-ferrocene) results in hydrogen... 

Skucas E, Ngai M-Y, Komanduri V, Krische MJ (2007) EnantiomericaUy enriched allylic alcohols and allylic amines via C-C bond forming hydrogenation asymmetric carbonyl and imine vinyla-tion. Acc Chem Res 40 1394-1401... 

Bower JF, Skucas E, Patman RL, Krische MJ (2007) Catalytic C-C coupling via transfer hydrogenation reverse prenylation, crotylation and allylation from the alcohol or aldehyde oxidation level. J Am Chem Soc 129 15134—15135... 

Liang T, Nguyen KD, Zhang W, Krische MI (2015) Enantioselective ruthenium-catalyzed carbonyl allylation via alkyne-alcohol C-C bond forming transfer hydrogenation aUene hydrometallation vs. oxidative coupling. J Am Chem Soc 137 3161-3164... 

Liang T, Zhang W, Chen T-Y, Nguyen KD, Krische MJ (2015) Ruthenium-catalyzed diastereo- and enantioselective coupling of propargyl ethers with alcohols siloxy-crotylation via hydride shift enabled conversion of alkynes to ji-allyls. J Am Chem Soc 137 13066-13071... 

Krische and co-workers reported an intramolecular version of the tandem conjugate addition-aldol reaction. Enone-ketone 59 reacts with phenylboronic add (2m) in dioxane containing 5 equiv. of water [40] (Scheme 4.26). This cyclization probably proceeds through the (oxa-7t-allyl)rhodium intermediate. Because the intramolecular addition of the intermediate to the ketone is faster than protonolysis with water, the al-dol product is obtained in high yields. Binap is a ligand of choice, leading to the conjugate addition-aldol product in up to 95% ee. 

T.P. Montgomery, A. Hassan, B.Y. Park, M.J. Krische, Enantioselective conversion of primary alcohols to a-exo-methylene y-butyrolactones via iridium-catalyzed C-C bond-forming transfer hydrogenation 2-(alkoxycarbonyl)allylation, J. Am. Chem. Soc. 134 (2012) 11100-11103. 

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