1568-65-6Relevant articles and documents
Enantioselective α-Allylation of Acyclic Esters Using B(pin)-Substituted Electrophiles: Independent Regulation of Stereocontrol Elements through Cooperative Pd/Lewis Base Catalysis
Scaggs, W. Rush,Snaddon, Thomas N.
, p. 14378 - 14381 (2018)
Cooperation between a Lewis base and Pd catalyst enables the direct enantioselective α-functionalization of aryl and vinyl acetic acid esters using a bifunctional B(pin)-substituted electrophile. Critical to the success of this method was the recognition that both catalysts could control the necessary stereochemical aspects; the Lewis base catalyst controls the enantioselectivity of the reaction, whereas the Pd catalyst regulates alkenyl-B(pin) configuration. This is the first example of using cooperative catalysis to control both stereochemical features during Pd-catalyzed allylic alkylation.
Total Syntheses of Echitamine, Akuammiline, Rhazicine, and Pseudoakuammigine
Zhang, Xiang,Kakde, Badrinath N.,Guo, Rui,Yadav, Sonyabapu,Gu, Yucheng,Li, Ang
, p. 6053 - 6058 (2019)
Echitamine (1) and akuammiline (2) are representative members of a fascinating class of monoterpenoid indole alkaloids. We report the syntheses of 2 and its congener deacetylakuammiline (3). The azabicyclo[3.3.1]nonane motif was assembled through silver-catalyzed internal alkyne cyclization, and one-pot C?O bond cleavage/C?N bond formation furnished the pentacyclic scaffold. Compound 3 then served as a common intermediate for preparing a series of structurally diverse and synthetically challenging congeners including 1. A position-selective Polonovski–Potier reaction followed by formal N-4 migration built the core of N-demethylechitamine (4) and 1. An alternative route featuring Meisenheimer rearrangement gave 4 as well. Oxidation of the alcohol within 3 gave rhazimal (5), which underwent tandem indolenine hydrolysis, hemiaminalization, and hemiketalization to form rhazicine (6). A sequence of N,O-ketalization and reductive amination secured the chemoselectivity of N-methylation, leading to pseudoakuammigine (7).
Enantioselective synthesis of α-quaternary Mannich adducts by palladium-catalyzed allylic alkylation: Total synthesis of(+)-sibirinine
Numajiri, Yoshitaka,Pritchett, Beau P.,Chiyoda, Koji,Stoltz, Brian M.
, p. 1040 - 1043 (2015)
A catalytic enantioselective method for the synthesis of -quaternary Mannich-type products is reported. The two-step sequence of (1) Mannich reaction followed by (2) decarboxylative enantioselective allylic alkylation serves as a novel strategy to in effect access asymmetric Mannich-type products of "thermodynamic"enolates of substrates possessing additional enolizable positions and acidic protons. Palladium-catalyzed decarboxylative allylic alkylation enables the enantioselective synthesis of five-, six-, and seven-membered ketone, lactam, and other heterocyclic systems. The mild reaction conditions are notable given the acidic free N-H groups and high functional group tolerance in each of the substrates. The utility of this method is highlighted in the first total synthesis of (+)-sibirinine.
Identification, syntheses, and characterization of the geometric isomers of 9,11-hexadecadienal from female pheromone glands of the sugar cane borer Diatraea saccharalis
Santangelo, Ellen M.,Coracini, Myrian,Witzgall, Peter,Correa, Arlene G.,Unelius, C. Rikard
, p. 909 - 915 (2002)
Chemical analysis of the pheromone glands of the sugar cane borer Diatraea saccharalis has shown the presence of the four geometric isomers of 9,11-hexadecadienal (1-4), in addition to hexadecanal and (Z)-hexadec-11-enal. We here report the syntheses and characterization of compounds 1-4, One starting material, 9-decen-1-ol, has been used to obtain all of them via divergent synthetic routes.
Brown,Gupta
, p. C1 (1971)
Gold-Catalyzed Photoredox C(sp2) Cyclization: Formal Synthesis of (±)-Triptolide
Cannillo, Alexandre,Schwantje, Travis R.,Bégin, Maxime,Barabé, Francis,Barriault, Louis
, p. 2592 - 2595 (2016)
Photoexcitation of a dimeric gold complex showed the activation of a C(sp2)-Br bond to generate a vinyl radical in a mild photoredox catalysis process. Use of [Au2(dppm)2]Cl2 with 365 nm LEDs in a photoredox catalysis process to produce polycyclic scaffolds using vinyl radicals is reported. This method achieved the synthesis of a small library of butenolide polycyclic compounds and naphthol polycyclic compounds. The efficacy of this photoredox process was further demonstrated by accomplishing the concise formal synthesis of (±)-triptolide.
Enantioselective Total Synthesis of the Guaianolide (-)-Dehydrocostus Lactone by Enediyne Metathesis
Kaden, Felix,Metz, Peter
supporting information, p. 1344 - 1348 (2021/02/20)
The hydroazulene core of the bioactive sesquiterpenoid (-)-dehydrocostus lactone was generated by domino enediyne metathesis. A triple hydroboration/oxidation of the resultant conjugated triene installed three out of four stereogenic centers of the target in a single step. The enantiopure acyclic metathesis substrate was readily available by an asymmetric anti aldol reaction. Masking of the O-lactone as an acetal allowed for an efficient completion of the synthesis through late-stage double carbonyl olefination.
Scalable, Durable, and Recyclable Metal-Free Catalysts for Highly Efficient Conversion of CO2 to Cyclic Carbonates
Li, Bo,Wu, Guang-Peng,Xie, Rui,Yang, Guan-Wen,Yang, Li,Zhang, Yao-Yao
supporting information, p. 23291 - 23298 (2020/10/19)
A series of highly active organoboron catalysts for the coupling of CO2 and epoxides with the advantages of scalable preparation, thermostability, and recyclability is reported. The metal-free catalysts show high reactivity towards a wide scope of cyclic carbonates (14 examples) and can withstand a high temperature up to 150 °C. Compared with the current metal-free catalytic systems that use mol % catalyst loading, the catalytic capacity of the catalyst described herein can be enhanced by three orders of magnitude (epoxide/cat.=200 000/1, mole ratio) in the presence of a cocatalyst. This feature greatly narrows the gap between metal-free catalysts and state-of-the-art metallic systems. An intramolecular cooperative mechanism is proposed and certified on the basis of investigations on crystal structures, structure–performance relationships, kinetic studies, and key reaction intermediates.
