126348-31-0Relevant academic research and scientific papers
Iron-Catalyzed Enantioselective Radical Carboazidation and Diazidation of α,β-Unsaturated Carbonyl Compounds
Dong, Shunxi,Feng, Xiaoming,He, Jun,Liu, Wen,Liu, Xiaohua,Pu, Maoping,Wu, Yun-Dong,Zhang, Tinghui
supporting information, p. 11856 - 11863 (2021/08/16)
Azidation of alkenes is an efficient protocol to synthesize organic azides which are important structural motifs in organic synthesis. Enantioselective radical azidation, as a useful strategy to install a C-N3 bond, remains challenging due to the inherently instability and unique structure of radicals. Here, we disclose an efficient enantioselective radical carboazidation and diazidation of α,β-unsaturated ketones and amides catalyzed by chiral N,N′-dioxide/Fe(OTf)2 complexes. An array of substituted alkenes was transformed to the corresponding α-azido carbonyl derivatives in good to excellent enantioselectivities, benefiting the preparation of chiral α-amino ketones, vicinal amino alcohols, and vicinal diamines. Control experiments and mechanistic studies proved the radical pathway in the reaction process. The DFT calculations showed that the azido transferred to the radical intermediate via an intramolecular five-membered transition state with the internal nitrogen of the Fe-N3 species.
Direct α-Acylation of Alkenes via N-Heterocyclic Carbene, Sulfinate, and Photoredox Cooperative Triple Catalysis
Liu, Kun,Studer, Armido
supporting information, p. 4903 - 4909 (2021/05/04)
N-Heterocyclic carbene (NHC) catalysis has emerged as a versatile tool in modern synthetic chemistry. Further increasing the complexity, several processes have been introduced that proceed via dual catalysis, where the NHC organocatalyst operates in concert with a second catalytic moiety, significantly enlarging the reaction scope. In biological transformations, multiple catalysis is generally used to access complex natural products. Guided by that strategy, triple catalysis has been studied recently, where three different catalytic modes are merged in a single process. In this Communication, direct α-C-H acylation of various alkenes with aroyl fluorides using NHC, sulfinate, and photoredox cooperative triple catalysis is reported. The method allows the preparation of α-substituted vinyl ketones in moderate to high yields with excellent functional group tolerance. Mechanistic studies reveal that these cascades proceed through a sequential radical addition/coupling/elimination process. In contrast to known triple catalysis processes that operate via two sets of interwoven catalysis cycles, in the introduced process, all three cycles are interwoven.
Preparation of Some Chromans Substituted at the 3- or 4-Position by an Aryl or Benzyl Group, by the Rhodium-catalysed Intramolecular Nucleophilic Substitution of the Corresponding 3-(2-Fluorophenyl)propanols
Houghton, Roy P.,Shervington, Leroy A.
, p. 1872 - 1892 (2007/10/02)
The bis(hexafluorophosphate) salt of the (η5-ethyltetramethylcyclopentadienyl)(η6-benzene)rhodium(III) cation has been used as a catalyst to prepare 3-phenyl-, 3-(4-methoxyphenyl)-, 3-(4-nitrophenyl)-, and 4-benzylchroman by cyclisation of the corresponding substituted 3-(2-fluorophenyl)-propanols in nitromethane-acetone solution. 3-Phenyl-4-hydroxymethylchroman and 3-hydroxymethyl-4-phenylchroman were prepared similarly.An attempt to prepare a bis(chroman) by a double cyclisation with 2-propane-1,3-diol afforded only the monochroman, 4-(2-fluorophenyl)-3-hydroxymethylchroman.Under the conditions of the cyclisation, the erythro and threo forms of 1,4-di(2-fluorophenyl)-butane-2,3-diol afforded only the corresponding 1,3-dioxolanes as the result of the diols reacting with the acetone used as cosolvent.The 1H n.m.r. spectra of the 3-substituted and 3,4-disubstituted chromans which have been prepared are consistent with the heterocyclic ring being in the half-chair conformation (6).
