34301-32-1Relevant academic research and scientific papers
Intermolecular Hydropyridylation of Unactivated Alkenes
Ma, Xiaoshen,Herzon, Seth B.
, p. 8718 - 8721 (2016)
A general method for the hydropyridylation of unactivated alkenes is described. The transformation connects metal-mediated hydrogen atom transfer to alkenes and Minisci addition reactions. The reaction proceeds under mild conditions with high site-selectivities and allows for the construction of tertiary and quaternary centers from simple alkene starting materials.
Cobalt bis(acetylacetonate)–tert-butyl hydroperoxide–triethyl-silane: A general reagent combination for the Markovnikov-selective hydrofunctionalization of alkenes by hydrogen atom transfer
Ma, Xiaoshen,Herzon, Seth B.
supporting information, p. 2259 - 2265 (2018/09/14)
We show that cobalt bis(acetylacetonate) [Co(acac)2], tert-butyl hydroperoxide (TBHP), and triethylsilane (Et3SiH) constitute an inexpensive, general, and practical reagent combination to initiate a broad range of Markovnikov-selective alkene hydrofunctionalization reactions. These transformations are believed to proceed by cobalt-mediated hydrogen atom transfer (HAT) to the alkene substrate, followed by interception of the resulting alkyl radical intermediate with a SOMOphile. In addition, we report the first reductive couplings of unactivated alkenes and aryldiazonium salts by an HAT pathway. The simplicity and generality of the Co(acac)2–TBHP–Et3SiH reagent combination suggests it as a useful starting point to develop HAT reactions in complex settings.
Hydroheteroarylation of Unactivated Alkenes Using N-Methoxyheteroarenium Salts
Ma, Xiaoshen,Dang, Hester,Rose, John A.,Rablen, Paul,Herzon, Seth B.
supporting information, p. 5998 - 6007 (2017/05/04)
We report the first reductive coupling of unactivated alkenes with N-methoxy pyridazinium, imidazolium, quinolinium, and isoquinolinium salts under hydrogen atom transfer (HAT) conditions, and an expanded scope for the coupling of alkenes with N-methoxy pyridinium salts. N-Methoxy pyridazinium, imidazolium, quinolinium, and isoquinolinium salts are accessible in 1-2 steps from the commercial arenes or arene N-oxides (25-99%). N-Methoxy imidazolium salts are accessible in three steps from commercial amines (50-85%). In total 36 discrete methoxyheteroarenium salts bearing electron-donating, electron-withdrawing, alkyl, aryl, halogen, and haloalkyl substituents were prepared (several in multigram quantities) and coupled with 38 different alkenes. The transformations proceed under neutral conditions at ambient temperature, provide monoalkylation products exclusively, and form a single alkene addition regioisomer. Preparatively useful and complementary site selectivities in the addition of secondary and tertiary radicals to pyidinium salts are documented: harder secondary radicals favor C-2 addition (2->10:1), while softer tertiary radicals favor bond formation to C-4 (4.7->29:1). A diene possessing a 1,2-disubstituted and 2,2-disubstituted alkene undergoes hydropyridylation at the latter exclusively (61%) suggesting useful site selectivities can be obtained in polyene substrates. The methoxypyridinium salts can also be employed in dehydrogenative arylation, borono-Minisci, and tandem arylation processes. Mechanistic studies support the involvement of a radical process.
N,N-Dimethylaminobenzoates enable highly enantioselective Sharpless dihydroxylations of 1,1-disubstituted alkenes
Zhao, Yaohong,Xing, Xiangyou,Zhang, Shaolong,Wang, David Zhigang
supporting information, p. 4314 - 4317 (2014/06/23)
A design scenario aimed at exploring beneficial catalyst-substrate π-π stacking electronic interactions in the classical Sharpless asymmetric dihydroxylations (SAD) leads to the identification of highly polarizable allylic N,N-dimethylaminobenzoate as a remarkably efficient auxiliary for inducing high levels of enantioselectivities (up to 99% ee) in the traditionally challenging substrate class of 1,1-disubstituted aliphatic alkenes. the Partner Organisations 2014.
Total synthesis and absolute configuration of avenolide, extracellular factor in Streptomyces avermitilis
Uchida, Miho,Takamatsu, Satoshi,Arima, Shiho,Miyamoto, Kiyoko T,Kitani, Shigeru,Nihira, Takuya,Ikeda, Haruo,Nagamitsu, Tohru
experimental part, p. 781 - 787 (2012/06/16)
The first total synthesis of extracellular factor, Avenolide, in Streptomyces avermitilis has been achieved using a convergent approach. The stereogenic centers in two key segments were installed using Sharpless epoxidation and dihydroxylation. This synthetic study allowed the determination of the absolute configuration of avenolide as 4S,10R, and yielded important information on its structure-activity relationship.
The application of a mechanistic model leads to the extension of the sharpless asymmetric dihydroxylation to allylic 4-methoxybenzoates and conformationally related amine and homoallylic alcohol derivatives
Corey,Guzman-Perez, Angel,Noe, Mark C.
, p. 10805 - 10816 (2007/10/03)
The scope and utility of the Sharpless asymmetric dihydroxylation has been expanded to include the use of allylic 4-methoxybenzoates as precursors of a wide variety of substituted chiral glycerol derivatives. The allylic 4-methoxybenzoyl group was found to be superior to other allylic alcohol protecting groups with respect to both yield and enantiomeric purity of the product. For example, asymmetric dihydroxylation of allyl 4-methoxybenzoate (6a) using the (DHQD)2PYDZ·OsO4 (1·OsO4) catalyst system affords (S)-3-(4-methoxybenzoyloxy)-1,2-propanediol (7a) in >99% yield and 98% ee. The 4-methoxybenzoates of a variety of other allylic alcohols also serve as excellent substrates, in contrast to the parent alcohols themselves. The efficient asymmetric dihydroxylation of homoallylic 4-methoxyphenyl ethers (12a and 15), allyl 9-fluorenimine (18b), bis(homoallyl) 4-methoxybenzoate (14) and other structurally related substrates is also described. This methodology was developed under mechanistic guidance from the transition state model advanced earlier by us for the bis-cinchona alkaloid catalyzed asymmetric dihydroxylation reaction. The 4-methoxybenzoyl group functions not only to selectively protect one of the hydroxy groups of the product triol for subsequent synthetic manipulation but also to provide an extended binding group that participates in hydrophobic and aryl-aryl interactions with the U-shaped binding pocket of the (DHQD)2PYDZ·OsO4 catalyst (1·OsO4), thereby enhancing enantioselectivity.
