- Sterically controlled alkylation of arenes through iridium-catalyzed C-H borylation
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Complementary chemistry: A one-pot method for the site-selective alkylation of arenes controlled by steric effects is reported. The process occurs through Ir-catalyzed C-H borylation, followed by Pd- or Ni-catalyzed coupling with alkyl electrophiles. This selectivity complements that of the typical Friedel-Crafts alkylation; meta-selective alkylation of a broad range of arenes with various electronic properties and functional groups occurs in good yield with high site selectivity. Copyright
- Robbins, Daniel W.,Hartwig, John F.
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supporting information
p. 933 - 937
(2013/02/25)
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- Versatile syntheses of alkynyl- and substituted alkynylcyclopropanes: 2-Alkoxyethynylcyclopropanes for the anellation of bicyclo[3.3.0]octane fragments
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Enol ethers 1a-f are brominated at -78°C and the resulting alkyl 1,2-dibromoethyl ethers are regioselectively coupled with propargylmagnesium bromide to give 4-alkoxy-5-bromo-1-pentynes 2a-f, which are protected at the acetylenic terminus with a trimethylsilyl group. These 4-alkoxy-5-bromo-1-trimethylsilyl-1-pentynes 3a-f readily cyclize by γ-elimination to give trimethylsilyl protected 2-alkoxyethynylcyclopropanes 4a-f in excellent overall yields. Under appropriate conditions (E)-diastereomers (E)-4a-f can be prepared selectively. The diastereoselectivity of the bromine addition onto enantiomerically pure chiral enol ethers 1e and 1f, however, is 64% (for 2f) at best. 2-Alkoxy-1-trimethylsilylethynylcyclopropanes(E/Z)-4 can be deprotonated with LDA or butyllithium to give configurationally stable 1-lithio derivatives (E)-6, which are trapped by reactive electrophiles (protons, carbonyl compounds, tosyl halides) with retention of configuration on the three-membered ring. 2-Alkoxy-1-ethynylcyclopropanes 5 can be used to anellate a bicyclo[3.3.0]octane fragment onto a cycloalkene in a domino-type reaction sequence, as demonstrated by the Pauson-Khand cycloaddition of(E)-5c to norbornene (14) as well as deltacyclene (20), and subsequent interconversion to the tetracyclic and hexacyclic compounds anti/syn-19 and anti/syn-25/27 with a reasonable degree of diastereoselectivity.
- Militzer,Schomenauer,Otte,Puls,Hain,Brase,De Meijere
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p. 998 - 1012
(2007/10/02)
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- NEW PREPARATION OF ALKYL IODIDES FROM THE CORRESPONDING ALCOHOLS
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It is shown that alkyl iodides can be obtained from the corresponding alkyl α-chloroethyl carbonate and NaI or by direct reaction between the alcohol, α-chloroethyl chloroformate and NaI.
- Brunet, J. J.,Laurent, H.,Caubere, P.
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p. 5445 - 5446
(2007/10/02)
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- α-NITRO SULFONES. 2. CONVENIENT NEW SYNTHESIS AND SELECTED FUNCTIONAL GROUP TRANSFORMATIONS
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(Phenylsulfonyl)nitromethane (1) is preferentially C-alkylated by benzylic halides and primary alkyl iodides, affording secondary α-nitro sulfone products. α-Nitro sulfones are also obtained from the corresponding C-alkylation of allylic acetates in the presence of catalytic tetrakis(triphenylphosphine)palladium.The palladium(0)-catalyzed reaction is stereospecific for geranyl and neryl acetates and is also regioselective.Desulfonation of α-nitro sulfones is readily accomplished by light-induced reduction with 1-benzyl-1,4-dihydronicotinamide (BNAH).Reduction of secondary α-nitro sulfones with 20percent aqueous titanium(III) chloride affords nitriles.Oxidation with alkaline permanganate affords carboxylic acids.
- Wade, Peter A.,Hinney, Harry R.,Amin, Nayan V.,Vail, Peter D.,Morrow, Scott D.,et al.
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p. 765 - 770
(2007/10/02)
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