69611-02-5Relevant articles and documents
Diastereoselective Addition of Prochiral Nucleophilic Alkenes to α-Chiral N-Sulfonyl Imines
Ando, Kaori,Fettinger, James,Gutierrez, David A.,Houk, K. N.,Shaw, Jared T.
supporting information, p. 1164 - 1168 (2022/02/14)
The Lewis-acid-promoted addition of prochiral E- and Z-allyl nucleophiles to chiral α-alkoxy N-tosyl imines is described. Alkene geometry is selectively transferred to the newly formed carbon-carbon bond, resulting in stereochemical control of C1, C2, and C3 of the resulting 2-alkoxy-3-N-tosyl-4-alkyl-5-hexene products. A computational analysis to elucidate the high selectivity is also presented. This methodology was employed in the synthesis of two naturally occurring isomers of clausenamide.
Selecting double bond positions with a single cation-responsive iridium olefin isomerization catalyst
Camp, Andrew M.,Kita, Matthew R.,Blackburn, P. Thomas,Dodge, Henry M.,Chen, Chun-Hsing,Miller, Alexander J.M.
, p. 2792 - 2800 (2021/03/01)
The catalytic transposition of double bonds holds promise as an ideal route to alkenes of value as fragrances, commodity chemicals, and pharmaceuticals; yet, selective access to specific isomers is a challenge, normally requiring independent development of different catalysts for different products. In this work, a single cation-responsive iridium catalyst selectively produces either of two different internal alkene isomers. In the absence of salts, a single positional isomerization of 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity and stereoselectivity. The same catalyst, in the presence of Na+, mediates two positional isomerizations to produce 3-alkenes. The synthesis of new iridium pincer-crown ether catalysts based on an aza-18-crown-6 ether proved instrumental in achieving cation-controlled selectivity. Experimental and computational studies guided the development of a mechanistic model that explains the observed selectivity for various functionalized 1-butenes, providing insight into strategies for catalyst development based on noncovalent modifications.
Nickel-Catalysed Allylboration of Aldehydes
Dennis, Francesca M.,Partridge, Benjamin M.,Robertson, Craig C.
, p. 1903 - 1914 (2020/07/04)
A nickel catalyst for the allylboration of aldehydes is reported, facilitating the preparation of homoallylic alcohols in high diastereoselectivity. The observed diastereoselectivities and NMR experiments suggest that allylation occurs through a well-defined six-membered transition state, with nickel acting as a Lewis acid.
Guanidine–Copper Complex Catalyzed Allylic Borylation for the Enantioconvergent Synthesis of Tertiary Cyclic Allylboronates
Ge, Yicen,Cui, Xi-Yang,Tan, Siu Min,Jiang, Huan,Ren, Jingyun,Lee, Nicholas,Lee, Richmond,Tan, Choon-Hong
supporting information, p. 2382 - 2386 (2019/02/01)
An enantioconvergent synthesis of chiral cyclic allylboronates from racemic allylic bromides was achieved by using a guanidine–copper catalyst. The allylboronates were obtained with high γ/α regioselectivities (up to 99:1) and enantioselectivities (up to 99 % ee), and could be further transformed into diverse functionalized allylic compounds without erosion of optical purity. Experimental and DFT mechanistic studies support an SN2′ borylation process catalyzed by a monodentate guanidine–copper(I) complex that proceeds through a special direct enantioconvergent transformation mechanism.
Selective Isomerization of Terminal Alkenes to (Z)-2-Alkenes Catalyzed by an Air-Stable Molybdenum(0) Complex
Becica, Joseph,Glaze, Owen D.,Wozniak, Derek I.,Dobereiner, Graham E.
, p. 482 - 490 (2018/02/17)
Positional and stereochemical selectivity in the isomerization of terminal alkenes to internal alkenes is observed using the cis-Mo(CO)4(PPh3)2 precatalyst. A p-toluenesulfonic acid (TsOH) cocatalyst is essential for catalyst activity. Various functionalized terminal alkenes have been converted to the corresponding 2-alkenes, generally favoring the Z isomer with selectivity as high as 8:1 Z:E at high conversion. Interrogation of the catalyst initiation mechanism by 31P NMR reveals that cis-Mo(CO)4(PPh3)2 reacts with TsOH at elevated temperatures to yield a phosphine-ligated Mo hydride (MoH) species. Catalysis may proceed via 2,1-insertion of a terminal alkene into a MoH group and stereoselective β-hydride elimination to yield the (Z)-2-alkene.
Synthesis and biological activity evaluation of dolastatin 10 analogues with N-terminal modifications
Wang, Xin,Dong, Suzhen,Feng, Dengke,Chen, Yazhou,Ma, Mingliang,Hu, Wenhao
supporting information, p. 2255 - 2266 (2017/03/24)
We have described the synthesis of the two complex units (2R,3R,4S)-dolaproine (Dap) and (3R,4S,5S)-dolaisoleuine (Dil) of dolastatin 10 from natural amino acids. The stereoselective syntheses of N-Boc-Dap (4a) and N-Boc-(2S)-iso-Dap (4b) were performed by employing crotylation of N-Boc-L-prolinal as a key step. Barbier-type allylation of N-Boc-L-isoleucinal provided a mild and convenient approach for the synthesis of N-Boc-Dil (5a) and N-Boc-(3S)-iso-Dil (5b). Ten dolastatin 10 analogues have been designed and synthesized with N-terminal modifications based on the known compound monomethylauristatin F (MMAF, 3). In comparison with MMAF (3), four of the compounds showed enhanced potency against HCT 116 human colon cancer cells in?vitro.
An alternative mechanism for the cobalt-catalyzed isomerization of terminal alkenes to (Z)-2-alkenes
Schmidt, Anastasia,N??dling, Alexander R.,Hilt, Gerhard
supporting information, p. 801 - 804 (2015/03/04)
The cobalt-catalyzed selective isomerization of terminal alkenes to the thermodynamically less-stable (Z)-2-alkenes at ambient temperatures takes place by a new mechanism involving the transfer of a hydrogen atom from a Ph2PH ligand to the starting material and the formation of a phosphenium complex, which recycles the Ph2PH complex through a 1,2-H shift.
Enantioselective synthesis of anti homoallylic alcohols from terminal alkynes and aldehydes based on concomitant use of a cationic iridium complex and a chiral phosphoric acid
Miura, Tomoya,Nishida, Yui,Morimoto, Masao,Murakami, Masahiro
, p. 11497 - 11500 (2013/09/02)
We report a highly diastereo- and enantioselective synthesis of anti homoallylic alcohols from terminal alkynes via (E)-1-alkenylboronates based upon two catalytic reactions: a cationic iridium complex-catalyzed olefin transposition of (E)-1-alkenylboronates and a chiral phosphoric acid-catalyzed allylation reaction of aldehydes.
SYNTHESIS OF BORONIC ESTERS AND BORONIC ACIDS USING GRIGNARD REAGENTS
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Paragraph 0088, (2013/03/26)
Boronic esters and boronic acids are synthesized at ambient temperature in an ethereal solvent by the reaction of Grignard reagents with a boron-containing substrate. The boron-containing substrate may be a boronic ester such as pinacolborane, neopentylglycolborane, or a dialkylaminoborane compound such as diisopropylaminoborane. The Grignard reagents may be preformed or generated from an alkyl, alkenyl, aryl, arylalkyl, heteroaryl, vinyl, or allyl halide compound and Mg°. When the boron-containing substrate is a boronic ester, the reactions generally proceed at room temperature without added base in about 1 to 3 hours to form a boronic ester compound. When the boron-containing substrate is a dialkylaminoborane compound, the reactions generally proceed to completion at 0°C in about 1 hour to form a boronic acid compound.
Enantioselective rhodium-catalyzed nucleophilic allylation of cyclic imines with allylboron reagents
Luo, Yunfei,Hepburn, Hamish B.,Chotsaeng, Nawasit,Lam, Hon Wai
supporting information; experimental part, p. 8309 - 8313 (2012/09/07)
Chiral allylrhodium nucleophiles: The highly diastereo- and enantioselective title reaction of a range of cyclic imines with various potassium allyltrifluoroborates most likely proceeds via allylrhodium(I) intermediates, and represents the first rhodium-catalyzed enantioselective nucleophilic allylation of π electrophiles with allylboron compounds. Copyright
