52323-92-9Relevant academic research and scientific papers
Zn- And Cu-catalyzed coupling of tertiary alkyl bromides and oxalates to forge challenging C?O, C?S, and C?N bonds
Gong, Yuxin,Zhu, Zhaodong,Qian, Qun,Tong, Weiqi,Gong, Hegui
supporting information, p. 1005 - 1010 (2021/02/01)
We describe here the facile construction of sterically hindered tertiary alkyl ethers and thioethers via the Zn(OTf)2catalyzed coupling of alcohols/phenols with unactivated tertiary alkyl bromides and the Cu(OTf)2-catalyzed thiolation of unactivated tertiary alkyl oxalates with thiols. The present protocol represents one of the most effective unactivated tertiary C(sp3)? heteroatom bond-forming conditions via readily accessible Lewis acid catalysis that is surprisingly less developed.
A well-defined (POCOP)Rh catalyst for the coupling of aryl halides with thiols
Timpa, Samuel D.,Pell, Christopher J.,Ozerov, Oleg V.
supporting information, p. 14772 - 14779 (2015/01/16)
This article describes a well-defined pincer-Rh catalyst for C-S cross-coupling reactions. (POCOP)Rh(H)(Cl) serves as an active precatalyst for the coupling of aryl chlorides and bromides with aryl and alkyl thiols under reasonable conditions (3% mol cat., 110 °C, 2-24 h, >90% yield). For select substrates, >90% yields were obtained with catalyst loading as low as 0.1%. Key mechanistic intermediates have been isolated and fully characterized, including (POCOP)Rh(Ph)(SPh) (6a) and (POCOP)Rh(SPh2) (6b). The aryl/bis(phosphinite) (POCOP)Rh system has been shown to favor aryl thiolate reductive elimination at elevated temperatures and in some cases at room temperature, compared with the analogous diarylamido/bis(phosphine) (PNP)Rh pincer system. Concerted reductive elimination has been studied with 6a directly and in the presence of aryl bromide and aryl chloride traps. This investigation demonstrates a clear rate dependence on aryl chloride concentration during catalysis, a dependence that is absent when using aryl bromides. The rate of catalysis is dramatically reduced or brought to zero for ortho-tolyl halides, which can be traced to slower C-S coupling and slower carbon-halogen oxidative addition for ortho-substituted aryls. The influence of the sterics in the thiol component is less straightforward. The S-H oxidative addition product (POCOP)Rh(H)(SPh) (16) has been fully characterized and its reactivity has been examined, resulting in the isolation of the sodium-thiolate adduct (POCOP)Rh(NaSPh) (19). The solid-state structure of 19 shows Na interactions not only with sulfur, but also with a neighboring Rh and the chelating aryl carbon of the pincer framework. The reactivity of 16 and 19 indicates that these potential side products should not hinder catalysis.
Metallation reactions. XXV. A re-examination of the metallation reaction of (alkylthio)fluorobenzenes
Cabiddu,Cabiddu,Cadoni,Fattuoni,Melis
, p. 97 - 106 (2007/10/03)
The metallation of (alkylthio)fluorobenzenes by organolithium compounds, lithium amides and butyllithium/potassium tert-butoxide superbasic mixture was re-examined. To avoid the formation of defluorinated compounds all the reactions must be carried out below -80°C. The para-substituted 1a and 1b showed a regiochemistry directed by the halogen; the ortho-derivative 1c underwent metallation ortho to the halogen when treated with lithium tetramethylpiperidide, an α-metallation with butyllithium while sec-butyllithium was less selective. Compounds 1a and 1c allowed the preparation of disubstituted products. At temperatures higher than -80°C increasing amounts of dehalogenated products are formed, whose formation can be explained through the intermediacy of arynes.
Long-range coupling constants for α-13C nuclei in phenyl-X-R (X = O,S,Se,Te) derivatives. Internal rotational information
Schaefer, Ted,Penner, Glenn H.
, p. 1641 - 1646 (2007/10/02)
The longrange spin-spin coupling constant over six bonds between the 19F nucleus and the 13C nucleus in the side chain, 6J(C,F), is reported for 4-F-C6H4-X-R, where X = O, S and R = CH3,CH2CH3,CH(CH3) and C(CH3)3. 6J(C,F) depends on sin2θ, where θ is the angle by which the side chain twists out-of-plane about the Csp2-X bond.Exceptation values of sin2θ are obtained from 6J(C,F), yielding magnitudes of the apparent twofold barrier to rotation about the Csp2-X bond.In these terms, the most stable conformation is that for θ = 0 deg for all compounds, with the exception of R =C(CH3)3 and of X = S, R = CH(CH3)2; there is effectively free rotation about the Csp2-S bond is isopropyl 4-fluorophenyl sulfide in acetone-d6 solution.Good correlations exist between 6J(C,F) and a number of other molecular properties, including certain differences of ionization potentials of the molecular orbitals in the ether.In particular, the chemical shifts of C-4 are correlated with 6J(C,F).Because 5J(C,C), the coupling constant involving C-4, also depends on sin2θ, it is measured for the methyl and ethyl selenides and tellurides, as are other 13C,13C couplings involving a 13C nucleus in the side chain.The literature values for the 13C nuclear magnetic resonance chemical shifts in alkyl phenyl selenides and tellurides can be related to θ preferences and also allow estimates of the extrema in 5j(C,C).The resultant values of arcsin 2θ>1'2 for R=CH3 are is good agreement with estimates of θ obtained from electron diffraction patterns, photoelectron spectra, and nuclear magnetic resonance in the nematic phase.
