3900-93-4Relevant academic research and scientific papers
Metal-Free Hydrosilylation of Ketenes with Silicon Electrophiles: Access to Fully Substituted Aldehyde-Derived Silyl Enol Ethers
Roy, Avijit,Oestreich, Martin
supporting information, p. 8273 - 8276 (2021/05/11)
Little-explored hydrosilylation of ketenes promoted by main-group catalysts is reported. The boron Lewis acid tris(pentafluorophenyl)borane accelerates the slow uncatalyzed reaction of ketenes and hydrosilanes, thereby providing a convenient access to the new class of β,β-di- and β-monoaryl-substituted aldehyde-derived silyl enol ethers. Yields are moderate to high, and Z configuration is preferred. The corresponding silyl bis-enol ethers are also available when using dihydrosilanes. The related trityl-cation-initiated hydrosilylation involving self-regeneration of silylium ions is far less effective.
Electroreductive Carbofunctionalization of Alkenes with Alkyl Bromides via a Radical-Polar Crossover Mechanism
Zhang, Wen,Lin, Song
supporting information, p. 20661 - 20670 (2020/12/23)
Electrochemistry grants direct access to reactive intermediates (radicals and ions) in a controlled fashion toward selective organic transformations. This feature has been demonstrated in a variety of alkene functionalization reactions, most of which proceed via an anodic oxidation pathway. In this report, we further expand the scope of electrochemistry to the reductive functionalization of alkenes. In particular, the strategic choice of reagents and reaction conditions enabled a radical-polar crossover pathway wherein two distinct electrophiles can be added across an alkene in a highly chemo- and regioselective fashion. Specifically, we used this strategy in the intermolecular carboformylation, anti-Markovnikov hydroalkylation, and carbocarboxylation of alkenes - reactions with rare precedents in the literature - by means of the electroreductive generation of alkyl radical and carbanion intermediates. These reactions employ readily available starting materials (alkyl halides, alkenes, etc.) and simple, transition-metal-free conditions and display broad substrate scope and good tolerance of functional groups. A uniform protocol can be used to achieve all three transformations by simply altering the reaction medium. This development provides a new avenue for constructing Csp3-Csp3 bonds.
Highly enantioselective direct alkylation of arylacetic acids with chiral lithium amides as traceless auxiliaries
Stivala, Craig E.,Zakarian, Armen
supporting information; experimental part, p. 11936 - 11939 (2011/09/19)
A direct, highly enantioselective alkylation of arylacetic acids via enediolates using a readily available chiral lithium amide as a stereodirecting reagent has been developed. This approach circumvents the traditional attachment and removal of chiral auxiliaries used currently for this type of transformation. The protocol is operationally simple, and the chiral reagent is readily recoverable.
Anionic cyclization of olefinic alkyllithiums: Ring closure of terminally substituted 5-hexenyllithiums
Bailey, William F.,Gavaskar, Kaustubh V.
, p. 5957 - 5970 (2007/10/02)
A series of 5-hexenyllithiums having a phenyl, trimethylsilyl, or cyclopropyl substituent at the terminal [C(6)] alkene carbon have been prepared from the corresponding iodides by lithium-iodine exchange with t-butyllithium at -78°C. Although 6-alkyl-substituted 5-hexenyllithiums do not isomerize to five-membered rings upon warning, terminally substituted 5-hexenyllithiums bearing a moderately activating phenyl or trimethylsilyl group cleanly undergo a totally regiospecific 5-exo cyclization at sub-ambient temperatures to afford five membered rings bearing a CHRLi moiety that may be trapped with an electrophile to deliver high yields of functionalized product. Cyclization of 6-cyclopropyl-5-hexenyllithium is accompanied by ring opening of the three-membered ring.
Soft drugs: III. A new class of anticholinergic agents
Bodor,Woods,Raper,et al.
, p. 474 - 480 (2007/10/02)
A new class of antimuscarinic drugs was designed and synthesized. The compounds are 'soft' quaternary ammonium esters in which there is only one carbon atom separating the ester oxygen and the quaternary head. The compounds are potent anticholinergics when derived from hindered 'umbrella' acids and cholinergics when derivatives of simple aliphatic acids. The more potent anticholinergics have up to 10 times higher acetylcholine antagonist activity than atropine, but they have a much shorter duration of action. The compounds cleave hydrolytically with simultaneous destruction of the quaternary head. The compounds are promising as selective, local agents, particularly as inhibitors of eccrine sweating.
