Several reactions of 2-(5-phenyladamantyl) derivatives have been examined with the objective of determining the stereochemistry of addition of electrophiles to a trigonal center Ct carrying a full or partial negative charge. These reactions included the carbonation and bromination of the 2-lithioadamantane(s) attack at the zu face was found to be predominant. Methylation of 5-phenyl-2-adamantanone with either methyllithium or lithium dimethylcuprate gave mixtures of the methyl alcohols in which the E-isomer is the main product. Attempts to study the reactions of the enolate anion derived from the (E)- and (Z)-phenyl 2-(5-phenyladamantyl) ketones 7-Ph were not successful: bromination could not be forced at all, and methylation and protonation occur at oxygen. The enol ether and enol were studied also; brominations of these neutral species occur at the zu face. It is concluded that even the imposition of negative charge upon the trigonal center does not engender the type of hyperconjugation envisioned by Anh in the capture of electrophiles. Protonation of the enol ether led to an equilibrium mixture of ketones 7-Ph; protonation of the enol itself gave an excess of the E-isomer. Possible reasons for this unexpected outcome are discussed.
Synergistic Activation of Amides and Hydrocarbons for Direct C(sp
<sup>3</sup>
)–H Acylation Enabled by Metallaphotoredox Catalysis
作者:Geun Seok Lee、Joonghee Won、Seulhui Choi、Mu‐Hyun Baik、Soon Hyeok Hong
DOI:10.1002/anie.202004441
日期:2020.9.21
amides as stable and readily accessible acyl surrogates. N‐acylsuccinimides served as efficient acyl reagents for the streamlined synthesis of synthetically useful ketones from simple C(sp3)−H substrates. Detailed mechanistic investigations using both computational and experimental mechanistic studies were performed to construct a detailed and complete catalytic cycle. The origin of the superior reactivity
were faced with the synthesis of sterically hindered benzylic enol ethers. This issue was solved via the use of an intermolecular McMurry cross-coupling between an ester and a ketone. In this article, together with the synthesis of the chemiluminescent probe, the scope and limitations of this low valent titanium based carboncarbon double bond formation are discussed.
An Investigation of the Yang Photocyclization Reaction in the Solid State: Asymmetric Induction Studies and Crystal Structure−Reactivity Relationships
作者:Mordechai Leibovitch、Gunnar Olovsson、John R. Scheffer、James Trotter
DOI:10.1021/ja9823013
日期:1998.12.1
investigated in the solid state and solution. In both media, ketones bearing methyl substituents α to the benzoyl group undergo stereoselective Yang photocyclization to afford endo-arylcyclobutanols. Quantum yield and quenching studies in solution show that the reactions are efficient triplet-mediated processes. Asymmetric induction studies were carried out by providing the reactants with carboxylic acid
已在固态和溶液中研究了具有基本顺-4-叔丁基-1-苯甲酰基环己烷或 2-苯甲酰基金刚烷结构的 16 种酮的 Norrish/Yang II 型光化学。在这两种介质中,带有甲基取代基α到苯甲酰基的酮经历立体选择性阳光环化以提供内芳基环丁醇。溶液中的量子产率和猝灭研究表明,这些反应是有效的三重态介导过程。不对称诱导研究是通过为反应物提供羧酸取代基来进行的,“离子手性助剂”通过与旋光胺形成盐而连接到这些羧酸取代基上。溶液中的盐(总共 17 种)的辐照得到外消旋环丁醇,但在结晶状态下,获得了中等至接近定量的对映体过量。对 10 种中性酮和四种盐成功进行了单晶 X 射线衍射研究。这允许识别反应性γ-氢原子并...
Organocatalytic C−H Functionalization of Simple Alkanes
作者:Fen Su、Fengfei Lu、Kun Tang、Xiaokang Lv、Zhongfu Luo、Fengrui Che、Hongyan Long、Xingxing Wu、Yonggui Robin Chi
DOI:10.1002/anie.202310072
日期:2023.11.6
functionalization/acylation of strong aliphatic C(sp3)-H bonds is disclosed via an N-heterocyclic carbene (NHC)-catalyzed dehydrogenative coupling of aldehydes with simple alkanes. The inert aliphatic C−H bonds are efficiently cleaved through intermolecular hydrogen atom transfer, providing an alternative organocatalytic approach for alkane C−H functionalization under transition metal- and light free
delivers the triplet carbene by intersystem crossing (ISC). Singlet car-2 does not undergo ISC but reacts in the intermolecular insertion reactions into C–H bonds. Car-3 has an α-C–H bond next to the carbene center and reacts rapidly in the intramolecular C–H insertion reaction to deliver alkene, precluding its detection by fs-TA. However, the isolation of ketone photoproducts from 3 is highly indicative of