19509-49-0Relevant academic research and scientific papers
C-HALOGEN BOND FORMATION
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Paragraph 0111-0118, (2013/03/26)
Methods of halogenating a carbon containing compound having an sp3 C-H bond are provided. Methods of fluorinating a carbon containing compound comprising halogenation with Cl or Br followed by nucleophilic substitution with F are provided. Methods of direct oxidative C-H fluorination of a carbon containing compound having an sp3 C-H bond are provided. The halogenated products of the methods are provided.
Manganese porphyrins catalyze selective C-H bond halogenations
Liu, Wei,Groves, John T.
supporting information; experimental part, p. 12847 - 12849 (2010/11/05)
We report a manganese porphyrin mediated aliphatic C-H bond chlorination using sodium hypochlorite as the chlorine source. In the presence of catalytic amounts of phase transfer catalyst and manganese porphyrin Mn(TPP)Cl 1, reaction of sodium hypochlorite with different unactivated alkanes afforded alkyl chlorides as the major products with only trace amounts of oxygenation products. Substrates with strong C-H bonds, such as neopentane (BDE =～100 kcal/mol) can be also chlorinated with moderate yield. Chlorination of a diagnostic substrate, norcarane, afforded rearranged products indicating a long-lived carbon radical intermediate. Moreover, regioselective chlorination was achieved by using a hindered catalyst, Mn(TMP)Cl, 2. Chlorination of trans-decalin with 2 provided 95% selectivity for methylene-chlorinated products as well as a preference for the C2 position. This novel chlorination system was also applied to complex substrates. With 5α-cholestane as the substrate, we observed chlorination only at the C2 and C3 positions in a net 55% yield, corresponding to the least sterically hindered methylene positions in the A-ring. Similarly, chlorination of sclareolide afforded the equatorial C2 chloride in a 42% isolated yield. Regarding the mechanism, reaction of sodium hypochlorite with the MnIII porphyrin is expected to afford a reactive MnVO complex that abstracts a hydrogen atom from the substrate, resulting in a free alkyl radical and a MnIV-OH complex. We suggest that this carbon radical then reacts with a MnIV-OCl species, providing the alkyl chloride and regenerating the reactive MnVO complex. The regioselectivity and the preference for CH2 groups can be attributed to nonbonded interactions between the alkyl groups on the substrates and the aryl groups of the manganese porphyrin. The results are indicative of a bent [MnvO-H-C] geometry due to the C-H approach to the MnvO (dπ-pπ)* frontier orbital.
Stereodirecting effects in the characterization of ylide intermediates in reactions of singlet methylene with an allylic ether and an allylic chloride
Cubbage, Jerry W.,Edelbach, Brian L.,Kuen, Kan Shuh,DeLuca, JoAnn P.
, p. 9823 - 9834 (2007/10/03)
The stereodirecting effects of substrate substituents were examined in addition of 1:CH2 to the double bonds of 3-methoxycyclohexene (3a), 3-chlorocyclohexene (3b), and 3-methylcyclohexene (3c) in pentane solution at temperatures fro
Synthetic Applications of Metal Halides.Conversion of Cyclopropylmethanols into Homoallylic Halides.
McCormick, J.P.,Barton, Donald L.
, p. 2566 - 2570 (2007/10/02)
Magnesium and beryllium halides in refluxing diethyl ether effect the transformation of cyclopropylmethanols into homoallylic halides,in contrast to several other metal halides and Lewis acid/nucleophile combinations which were examined.Magnesium bromide and iodide are particularly effective: conditions are mild,yields are high,and little or no byproducts are formed.Tertiary and benzylic alcohols are more reactive than secondary alcohols,while the latter are converted into E homoallylic halides with high stereoselectivity.Cyclopropylmethanol itself fails to react.In the cases of magnesium halide reactions with bicyclo-2-hexanol and bicyclo-2-heptanol,addition of an equimolar amount of zinc halide not only caused substantial rate enhancement but also increased regioselectivity.
