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61.
Dr. Tian Qin Dr. Lara R. Malins Jacob T. Edwards Rohan R. Merchant Alexander J. E. Novak Jacob Z. Zhong Riley B. Mills Ming Yan Dr. Changxia Yuan Dr. Martin D. Eastgate Prof. Phil S. Baran 《Angewandte Chemie (International ed. in English)》2017,56(1):260-265
Two named reactions of fundamental importance and paramount utility in organic synthesis have been reinvestigated, the Barton decarboxylation and Giese radical conjugate addition. N ‐hydroxyphthalimide (NHPI) based redox‐active esters were found to be convenient starting materials for simple, thermal, Ni‐catalyzed radical formation and subsequent trapping with either a hydrogen atom source (PhSiH3) or an electron‐deficient olefin. These reactions feature operational simplicity, inexpensive reagents, and enhanced scope as evidenced by examples in the realm of peptide chemistry. 相似文献
62.
63.
In this critical review, the strategic and economic benefits of C-H functionalization logic will be analyzed through the critical lens of total synthesis. In order to illustrate the dramatically simplifying effects this type of logic can potentially have on synthetic planning, we take the reader through a series of case studies in which it has already been successfully applied. In the first section, a chronological look at key historical syntheses will be examined, leading into modern day examples. In the second section, our own experience with applying and executing synthesis with a C-H functionalization "mindset" will be discussed (114 references). 相似文献
64.
Fujiwara Y Domingo V Seiple IB Gianatassio R Del Bel M Baran PS 《Journal of the American Chemical Society》2011,133(10):3292-3295
A direct functionalization of a variety of quinones with several boronic acids has been developed. This scalable reaction proceeds readily at room temperature in an open flask using inexpensive reagents: catalytic silver(I) nitrate in the presence of a persulfate co-oxidant. The scope with respect to quinones is broad, with a variety of alkyl- and arylboronic acids undergoing efficient cross-coupling. The mechanism is presumed to proceed through a nucleophilic radical addition to the quinone with in situ reoxidation of the resulting dihydroquinone. This method has been applied to complex substrates, including a steroid derivative and a farnesyl natural product. 相似文献
65.
de Vargas-Sansalvador IM Fay C Phelan T Fernández-Ramos MD Capitán-Vallvey LF Diamond D Benito-Lopez F 《Analytica chimica acta》2011,(2):216-222
A new system for CO2 measurement (0–100%) based on a paired emitter–detector diode arrangement as a colorimetric detection system is described. Two different configurations were tested: configuration 1 (an opposite side configuration) where a secondary inner-filter effect accounts for CO2 sensitivity. This configuration involves the absorption of the phosphorescence emitted from a CO2-insensitive luminophore by an acid–base indicator and configuration 2 wherein the membrane containing the luminophore is removed, simplifying the sensing membrane that now only contains the acid–base indicator. In addition, two different instrumental configurations have been studied, using a paired emitter–detector diode system, consisting of two LEDs wherein one is used as the light source (emitter) and the other is used in reverse bias mode as the light detector. The first configuration uses a green LED as emitter and a red LED as detector, whereas in the second case two identical red LEDs are used as emitter and detector. The system was characterised in terms of sensitivity, dynamic response, reproducibility, stability and temperature influence. We found that configuration 2 presented a better CO2 response in terms of sensitivity. 相似文献
66.
Lee PH Mo J Kang D Eom D Park C Lee CH Jung YM Hwang H 《The Journal of organic chemistry》2011,76(1):312-315
Pd-catalyzed cross-coupling reactions of aryl iodides containing not only an electron-donating group but also an electron-withdrawing group on the aryl ring with organoindium reagents generated in situ from indium and ethyl 4-bromo-2-alkynoates produced selectively ethyl 2-aryl-2,3-alkadienoates in good yield. 相似文献
67.
A sweeping structural revision of the sarcodonin natural product family (published structures 1a-13a) is proposed after extensive studies aimed at their chemical synthesis. Key features of revised structure 1b include replacement of the N,N-dioxide moiety with an oxime, ring-opening of the central diketopiperazine, and transposition of the terphenyl wing from the 1β-2β position of 1a to the 2β-3β position of 1b. This structure revision arose from the serendipitous synthesis of a benzodioxane aminal (44) whose structure was unambiguously determined by X-ray crystallography and whose spectral properties bore considerable resemblance to the published data for the sarcodonins. A versatile new method for O-arylation of hydroxamic acids is also reported herein, as well as a manganese(III)-mediated α-oxidation of hydroxamic acids to aminals. 相似文献
68.
Pd-catalyzed multifold (2-, 3-, and 4-fold) carbon-sulfur cross-coupling reaction of indium tri(organothiolates) with polybromonated aromatic and heteroaromatic compounds was developed in a one-pot procedure. Both 2,5-dibromopyridine and 2,6-dibromopyridine reacted with indium tri(organothiolates) (0.68 equiv) in the presence of 4 mol % of Pd(OAc)(2), 4.2 mol % of Xantphos, and 1 equiv of diisopropylethylamine (DIPEA), producing disulfides in good to excellent yields. These results indicate that indium tri(organothiolates) transfer all three alkyl- or arylthio groups attached to indium metal to electrophilic coupling partners. Indium tri(organothiolates) derived from alkyl thiol having a low boiling point, such as n-propyl, isopropyl, and tert-butyl thiol, acted as good nucleophilic coupling partners. In addition, indium tri(arylthiolates) derived from aryl thiols possessing an electron-withdrawing or -donating group on the aromatic ring participated well in the Pd-catalyzed multifold carbon-sulfur cross-coupling reaction. 4,4'-Dibromo-1,1'-biphenyl, 9,10-dibromoanthracene, 2,4-dibromoanisole, 2,7-dibromo-9,9-dimethylfluorene, 3,4-dibromothiophene, 2,3-dibromothiophene, 2,2'-bithiophene, 1,3,5-tribromobenzene, and 1,2,4,5-tetrabromobenzene were converted smoothly to the corresponding di-, tri-, and tetrasulfides. 相似文献
69.
Quentin Michaudel Guillaume Journot Alicia Regueiro‐Ren Animesh Goswami Zhiwei Guo Thomas P. Tully Lufeng Zou Raghunath O. Ramabhadran Kendall N. Houk Phil S. Baran 《Angewandte Chemie (International ed. in English)》2014,53(45):12091-12096
Physicochemical properties constitute a key factor for the success of a drug candidate. Whereas many strategies to improve the physicochemical properties of small heterocycle‐type leads exist, complex hydrocarbon skeletons are more challenging to derivatize because of the absence of functional groups. A variety of C H oxidation methods have been explored on the betulin skeleton to improve the solubility of this very bioactive, yet poorly water‐soluble, natural product. Capitalizing on the innate reactivity of the molecule, as well as the few molecular handles present on the core, allowed oxidations at different positions across the pentacyclic structure. Enzymatic oxidations afforded several orthogonal oxidations to chemical methods. Solubility measurements showed an enhancement for many of the synthesized compounds. 相似文献
70.
Let ∑?n denote the nonorientable surface of nonorientable genus n. A graph G is irreducible for ∑?n if G does not embed in ∑?n but any proper subgraph does embed. Let I3∑?n) denote the set of cubic irreducible graphs for ∑?n. This note provesTheorem. I3(∑?n) is finite for eachn. 相似文献