Expeditious asymmetric synthesis of a stereoheptad corresponding to the C(19)-C(27)-ansa chain of rifamycins: Formal total synthesis of Rifamycin S
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In the presence of a Lewis or protic acid and at low temperature, 1,3-dioxy-1,3-dienes add to sulfur dioxide generating zwitterionic intermediates that can react with carbon nucleophiles such as allylsilanes. After a retro-ene elimination of SO2, valuable ...
2004
The energetics of dissocn. reactions of S82+ into stoichiometric mixts. of Sn+, n = 2-7, and Sm2+, m = 3, 4, 6, 10, were investigated by the B3PW91 method [6-311+G(3df)//6-311+G*] in the gas phase and in soln., with solvation energies calcd. using the SCIP ...
At low temperature, 1-alkoxy-1,3-dienes add to sulfur dioxide activated by a Lewis or protic acid generating zwitterionic intermediates that can be quenched by enoxysilanes. The resulting beta,gamma-unsaturated silyl sulfinates can be desilylated by 1:1 Pd ...
The reactivity of (E)- and (Z)-1-fluorobuta-1,3-diene ((E)- and (Z)-11), 2-fluorobutadiene (12). (E)and (Z)-1-(fluoromethylidene)-2-methylidenecyclohexane ((E)- and (Z)-13) toward SO2 has been explored and compared with that of (Z)- and (E)-1-(fluoromethyl ...
Chloroprene (= 2-chlorobuta-1,3-diene; 4b) and electron-rich dienes such as 2-methoxy-(4c), 2-acetoxy(dd), and 2-(phenylseleno)buta-1,3-diene (4e) refused to equilibrate with the corresponding sultines 5 or 6 between -80 and -10degrees in the presence of e ...
At low temperature 1-alkoxy-1,3-dienes add to sulfur dioxide activated by a Lewis or Bronstedt acid and generate zwitterionic intermediates that can be quenched by enoxysilanes. The resulting beta,gamma -unsaturated silyl sulfinates can be desilylated and ...
[Pt-3(mu-CO)(3)(PPh3)(3)] was prepared in high yield by the reaction of [Pt-3(mu-CO)(3)(PPh3)(4)] with H2O2. The carbonyl ligands in [Pt-3(mu-CO)(3)(PR3)(3)] (PR3 = PPh3, PPh(2)Bz, PCy3, P'Pr-3) may be completely replaced by sulfur dioxide to give [Pt-3(mu ...
Even unsubstituted butadiene adds to sulfur dioxide in the hetero-Diels Alder mode more rapidly than in the chelotropic mode. The sultine can be observed in equilibrium with the diene and the sulfur dioxide only at low temperature and in the presence of CF ...
The reactions of (E,E)-1-benzyloxy-2-methylpenta-1,3-diene (9) with 3,3-dimethyl-2-(trimethylsilyloxy)butene and (Z)-3-(trimethylsilyloxy)pent-2-ene in SO2 and a Lewis acid give silyl sulfinates that are quenched with Met to generate the corresponding (Z)- ...
The hetero-Diels-Alder addition of sulfur dioxide to (E)- and (Z)-4-(fluoromethylidene)-3-methylene-2,3-dihydro-naphthalene follows the endo Alder rule. The first example of a crystalline sultine has been obtained. In agreement with high level quantum calc ...
