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41.
[reaction: see text] Asymmetric aldol addition reactions have been conducted with (1R,2S)-ephedrine-derived 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one (2). Diastereoselectivities range from 75:25 to 99:1 for the formation of the crude non-Evans syn adducts 8a-h. The facial selectivity of the enolate is directed by the stereogenic N(4)-methyl substituent. Aldol adduct 8a is readily cleaved by acid hydrolysis to afford (2S,3S)-3-hydroxy-2-methyl-3-phenylpropionic acid (9) in >95% ee. 相似文献
42.
Shawn R. Hitchcock George P. Nora David M. Casper Joseph D. Wiman Jeromy T. Bentley Carrie Stafford Michael D. Squire 《Journal of heterocyclic chemistry》2002,39(5):1113-1115
A several novel 1,3,4‐oxadiazinan‐2‐thiones have been synthesized by the cyclization of β‐hydrazino‐alcohols with either carbon disulfide or 1,1′‐thiocarbonyldiimidazole (TCDI). 相似文献
43.
Westrup KC Gregório T Stinghen D Reis DM Hitchcock PB Ribeiro RR Barison A Back DF de Sá EL Nunes GG Soares JF 《Dalton transactions (Cambridge, England : 2003)》2011,40(13):3198-3210
The reversible thermochromic behaviour of homoleptic [{V(OR)(4)}(n)] complexes in solution [R = Pr(i) (product I), Bu(s) (B(s)), Nep (N) and Cy (C)] is accounted for the existence of an aggregation equilibrium involving dimeric and monomeric species in which vanadium(iv) is respectively five- and four-coordinate. Bulky R groups such as Bu(t) and Pe(t) (tert-pentoxide) prevent aggregation and therefore give rise to exclusively mononuclear compounds (B(t) and P(t), respectively) that are not thermochromic. The complexes and their temperature-dependent interconversion were characterised by single crystal X-ray diffractometry, magnetic susceptibility measurements and electronic, FTIR and EPR spectroscopies in a wide temperature range. Equilibrium constants and enthalpy and entropy changes for the dimerization reactions have been determined and compared with literature data. 相似文献
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Barbara Gehrhus Peter B. Hitchcock Helen Jansen 《Journal of organometallic chemistry》2006,691(4):811-816
Reaction of the thermally stable silylene Si[(NCH2But)2C6H4-1,2] (1) [abbrev. as Si(NN)] with SiX4 (X = Cl or Br) afforded the disilanes (NN)SiX(SiX3) and [(NN)SiX]2 (X = Br only), the trisilane (NN)SiX-[(SiX3)Si(NN)] and the monosilane (NN)SiX2 (X = Br only), whereas treatment of 1 with MCl4 (M = Ge or Sn) yielded (NN)SiCl2 and MCl2. [(NN)SiBr]2 and (NN)SiBr2 were also obtained by reaction of 1 with Br2. Reaction of 1 with PhSiCl3 yielded the disilane (NN)SiCl(SiCl2Ph) and trisilane [(NN)SiCl]2SiClPh, whereas the disilane (NN)SiCl(SiCl2Me) was obtained with MeSiCl3. The trisilane (NN)SiCl-[(SiCl3)Si(NN)] was thermally labile and converted to [(NN)SiCl]2SiCl2. 相似文献
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Peter B. Hitchcock 《Journal of organometallic chemistry》1981,218(1):C18-C20
The products formed in the reactions of CO2 and CO with the hexameric copper hydride [HCuPPh3]6 have been isolated and identified. Reactions of the formate (Ph3P)2CuOCOH, the product of CO2 insertion into the HCu bond, have also been studied. 相似文献