20157-19-1Relevant articles and documents
Copper Hydride Catalyzed Reductive Claisen Rearrangements
Wong, Kong Ching,Ng, Elvis,Wong, Wing-Tak,Chiu, Pauline
supporting information, p. 3709 - 3712 (2016/03/08)
An efficient reductive Claisen rearrangement, catalyzed by in situ generated copper hydride and stoichiometric in diethoxymethylsilane, has been developed. Yields of up to 95 ;% with good to excellent diastereoselectivities were observed in this reaction. Mechanistic studies showed that the stereospecific rearrangement proceeded via a chair transition state of (E)-silyl ketene acetals as intermediates and not via the copper enolates.
Accessing Both Retention and Inversion Pathways in Stereospecific, Nickel-Catalyzed Miyaura Borylations of Allylic Pivalates
Zhou, Qi,Srinivas, Harathi D.,Zhang, Songnan,Watson, Mary P.
supporting information, p. 11989 - 11995 (2016/10/07)
We have developed a stereospecific, nickel-catalyzed Miyaura borylation of allylic pivalates, which delivers highly enantioenriched α-stereogenic γ-aryl allylboronates with good yields and regioselectivities. Our complementary sets of conditions enable access to either enantiomer of allylboronate product from a single enantiomer of readily prepared allylic pivalate substrate. Excellent functional group tolerance, yields, regioselectivities, and stereochemical fidelities are observed. The stereochemical switch from stereoretention to stereoinversion largely depends upon solvent and can be explained by competitive pathways for the oxidative addition step. Our mechanistic investigations support a stereoretentive pathway stemming from a directed oxidative addition and a stereoinvertive pathway that is dominant when MeCN blocks coordination of the directing group by binding the nickel catalyst.
Catalytic asymmetric addition of aldehydes using organolithium reagents in the presence of commercial available chiral diol ligands
Zong, Hua,Huang, Huayin,Song, Ling
supporting information, p. 1069 - 1074 (2016/10/11)
An efficient method for the catalytic asymmetric additions to aldehydes using organolithium reagents and titanium(IV) isopropoxide in the presence of commercially available and relatively inexpensive diol ligands, such as (S)-BINOL or D-TADDOL has been developed. Good to excellent yields (up to 92%) and enantioselectivities (up to 94%) of the corresponding secondary alcohol products can be obtained following a simple procedure at relatively mild reaction temperatures.
Pd-Catalyzed stereospecific allyl-aryl coupling of allylic alcohols with arylboronic acids
Ye, Jiang,Zhao, Jingming,Xu, Jing,Mao, Yuxue,Zhang, Yong Jian
supporting information, p. 9761 - 9763 (2013/10/21)
An efficient method for Pd-catalyzed stereospecific allyl-aryl coupling of allylic alcohols with arylboronic acids has been described. The reactions proceeded smoothly in the presence of Pd2(dba)3· CHCl3 and racemic BINAP
Room temperature and highly enantioselective additions of alkyltitanium reagents to aldehydes catalyzed by a titanium catalyst of (R)-h 8-binol
Li, Qinghan,Gau, Han-Mou
experimental part, p. 929 - 939 (2012/06/29)
Three alkyltitanium reagents of RTi(O-i-Pr)3 (R = Cy (1a), i-Bu (1b), and n-Bu (1c)) were prepared in good yields. The high-resolution mass spectroscopy showed that 1b and 1c in the gas phase are monomeric species. However, the solid state of 1a revealed a dimeric structure. Asymmetric additions of 1a-1c to aldehydes catalyzed by a titanium catalyst of (R)-H 8-BINOL were studied at room temperature. The reactions produced desired secondary alcohols in good yields with good to excellent enantioselectivities of up to 94% ee. Reactivity and enantioselectivity differences, in terms of steric bulkiness of the R nucleophiles, are herein described. The addition reactions of secondary c-hexyl to aldehydes were slower than the reactions of primary i-butyl or n-butyl nucleophiles. For the primary alkyls, lower enantioselectivities were obtained for products from addition reactions of the linear n-butyl as compared with the enantioselectivities of products from the addition reactions of the branched i-butyl group. The same stereochemistry of RTi(O-i-Pr)3 addition reactions as the addition reactions of organozinc, organoaluminum, Grignard, or organolithium reagents directly supports the argument of that titanium-catalyzed addition reactions of aldehydes involve an addition of an organotitanium nucleophile.
Palladium-catalyzed γ-selective and stereospecific allyl-aryl coupling between acyclic allylic esters and arylboronic acids
Ohmiya, Hirohisa,Makida, Yusuke,Li, Dong,Tanabe, Masahito,Sawamura, Masaya
supporting information; experimental part, p. 879 - 889 (2010/03/25)
Reactions between acyclic (E)-allylic acetates and arylboronic acids in the presence of a palladium catalyst prepared from Pd(OAc)2, phenanthroline (or bipyridine), and AgSbF6 (1:1.2:1) proceeded with excellent γ-selectivity to afford allyl-aryl coupling products with E-configuration. The reactions of α-chiral allylic acetates took place with excellent α-to-γ chirality transfer with syn stereochemistry to give allylated arenes with a stereogenic center at the benzylic position. The reaction tolerated a broad range of functional groups in both the allylic acetates and the arylboronic acids. Furthermore, γ-arylation of cinnamyl alcohol derivatives afforded gem-diarylalkane derivatives containing an unconjugated alkenic substituent. The synthetic utility of this method was demonstrated by its utilization in an efficient synthesis of (+)-sertraline, an antidepressant agent. The observed γ-regioselectivity and E-1,3-syn stereochemistry were rationalized based on a Pd(II) mechanism involving transmetalation between a cationic mono(acyloxo)palladium(II) complex and arylboronic acid, and directed carbopalladation followed by syn-β-acyloxy elimination. The results of stoichiometric reactions of palladium complexes related to possible intermediates were fully consistent with the proposed mechanism.
Enantioselective addition of alkenylzinc reagents to aldehydes with organoboronates as the alkenyl source
Chai, Zhuo,Liu, Xin-Yuan,Zhang, Jun-Kang,Zhao, Gang
, p. 724 - 728 (2008/02/01)
Alkenylboronates were used as a vinyl source in the asymmetric addition of an alkenylzinc reagent to aldehydes catalyzed by a dendritic ligand. The resulting allylic alcohol products were obtained in 66-96% ee and 35-64% yields.
Application of organocerium reagents for the efficient conversion of Z-α,β-unsaturated Weinreb amides to Z-α,β-unsaturated ketones
Kojima, Satoshi,Hidaka, Tsugihiko,Yamakawa, Atsushi
, p. 470 - 471 (2007/10/03)
The reactions of Z-rich unsaturated Weinreb amides with organolithium and organocerium reagents were examined. Taking in consideration both the extent of geometry retention and cleanness of the reaction, organocerium reagents were more effective for the conversion to Z-α,β-unsaturated ketones. Copyright
A novel tandem Michael addition/Meerwein-Ponndorf-Verley reduction: Asymmetric reduction of acyclic α,β-unsaturated ketones using a chiral mercapto alcohol
Node, Manabu,Nishide, Kiyoharu,Shigeta, Yukihiro,Shiraki, Hiroaki,Obata, Kenichi
, p. 1927 - 1936 (2007/10/03)
The introduction of a thiol group into a chiral alcohol reagent for asymmetric Meerwein-Ponndorf-Verley (MPV) reductions allows asymmetric reduction of α,β-unsaturated ketones to secondary alcohols and allylic alcohols via a novel tandem Michael addition/MPV reduction. The reaction of acyclic α,β-unsaturated ketones 1 and an optically active 1,3-mercapto alcohol (-)-2 using dimethylaluminum chloride afforded the MPV reduction products 3 diastereoselectively in very high yields (up to 96%). Mechanistic studies elucidated (1) the structure of the chelation complex D with (-)-2 and Me2AlCl, (2) an asymmetric 1,7-hydride shift (intramolecular MPV reduction), and (3) dynamic kinetic resolution via reversible Michael addition. Subsequent reductive desulfurization of the MPV products 3 with a modified Raney nickel system led to the highly enantioselective reduction of α,β-unsaturated ketones to saturated secondary alcohols in 96-98% ee. β-Elimination of the corresponding sulfoxides gave the allylic alcohols in 86-98% ee. Applications to the asymmetric reduction of a synthetic intermediate 1m of prostaglandins and to a new asymmetric synthesis of the (+)-Rove beetle pheromone 11 are described.
