Palladium-Catalyzed Reductive Coupling of Acid Chlorides with .beta.-Stannyl Enones: Synthesis of 1,4-Diketones and Mechanistic Aspects
摘要:
The palladium-catalyzed coupling of acid chlorides with (E)-1,2-bis(tri-n-butylstannyl)ethene or beta-stannyl enones gives butane-1,4-diones directly by reduction of the intermediate enedicarbonyl intermediate. The double bond conjugated with a single carbonyl group was not significantly reduced. The generality of the method is illustrated by two syntheses of the 1,4-diketone ipomeanine. By performing the reaction at lower temperatures, alpha,beta-unsaturated 1,4-diketones can also be prepared. The reduction of the intermediate alpha,beta-unsaturated 1,4-diketones probably proceeds by insertion of a palladium hydride, formed in situ by reaction of a Pd(II) complex with Bu(3)SnCl, followed by hydrolysis of the intermediate palladium enolate.
The first totalsynthesis of lajollamycin B, a structurally novel nitro‐tetraene spiro‐β‐lactone/γ‐lactone antibiotic, is described. The convergent synthesis involves the construction of the C8′–C11′ nitrodienylstannane and its coupling with the segment prepared from the C1′–C7′ ω‐iodoheptadienoic acid and the right‐hand heterocyclic fragment, which has been utilized for our previous syntheses of oxazolomycin A
Regioselective Formation of (
<i>E</i>
)‐β‐Vinylstannanes with a Topologically Controlled Molybdenum‐Based Alkyne Hydrostannation Catalyst
作者:Kyle A. Mandla、Curtis E. Moore、Arnold L. Rheingold、Joshua S. Figueroa
DOI:10.1002/anie.201802397
日期:2018.6.4
long‐standing challenge in transition‐metal‐catalyzed alkynehydrostannation. Herein, we report a well‐defined molybdenum‐based system featuring two encumbering m‐terphenyl isocyanides that reliably and efficiently delivers (E)‐β‐vinylstannanes from a range of terminal and internal alkynes with high regioselectivity. The system is particularly effective for aryl alkynes and can discriminate between alkyl chains
The enantioselectivetotalsyntheses of (+)-decursin (1) and related natural dihydropyranocoumarins (−)-prantschimgin (3), (+)-decursinol (4), and (+)-marmesin (5) were achieved for the first time using catalytic asymmetric epoxidation of an enone as the key step. Catalytic asymmetric epoxidation of the enone was effectively promoted by the novel multifunctional asymmetric catalyst generated from La(O-i-Pr)3
首次实现(+)-地精(1)和相关天然二氢吡喃香豆素(-)-花木素(3),(+)-地精醇(4)和(+)-marmesin(5)的对映选择性合成使用烯酮的催化不对称环氧化作为关键步骤。由La(O- i- Pr)3,BINOL和Ph 3 As generatedO以1:1:1的比例生成的新型多功能不对称催化剂可有效促进烯酮的催化不对称环氧化,以94%的收率得到环氧化物和96%ee,将其重结晶得到光学纯的环氧化物。转换为通用关键中间体(-)-二十二烷醇(7),所有天然的二氢吡喃香豆素都是通过钯催化的分子内C-O偶联反应合成的。基于X射线分析,激光解吸/电离飞行时间质谱,动力学研究和不对称扩增研究,还描述了烯类催化不对称环氧化的可能反应机理。
The stannyl–cupration of acetylenes and the reaction of the intermediate cuprates with electrophiles as a synthesis of substituted vinylstannanes
作者:Asunción Barbero、Purificación Cuadrado、Ian Fleming、Ana M. González、Francisco J. Pulido
DOI:10.1039/c39920000351
日期:——
Stannyl–cupration of acetylenes followed by electrophilic attack with a variety of electrophiles gives vinylstannanes.
Base-Functionalized Carbocyclic Nucleosides: Design, Synthesis, and Mechanism of Antiviral Activity
作者:Vasu Nair、Fan Zhang、Xiaohui Ma、Eric Bonsu
DOI:10.1080/15257770903044465
日期:2009.8.11
nucleobase were designed as potential RNA antiviral compounds. The design was based on the expectation that the monophosphates of these compounds would be inhibitors of the enzyme, IMPDH. Appropriate methodologies were developed to achieve the target molecules. Results from the initial in vitro antiviral studies are mentioned. The IMPDH-associated mechanism of the antiviralactivity of the most active