Regio- and stereoselective carbometallation reactions of N-alkynylamides and sulfonamides

• Yury Minko,
• Morgane Pasco,
• Helena Chechik and
• Ilan Marek

Beilstein J. Org. Chem. 2013, 9, 526–532, doi:10.3762/bjoc.9.57

• : carbometallation; enamides; organocopper; regiochemistry; ynamides; Introduction Due to a strong differentiation of electron density on the two sp-hybridized carbon atoms, N-alkynylamides (ynamides) have become attractive substrates involved in many synthetically useful transformations [1][2][3][4]. The

• -addition of the organocopper reagent on the triple bond [23], the regioselectivity is dependent on the nature of the α-substituent on the alkyne 1. The presence of a donor substituent (XR = OR, NR2, Path B, Scheme 1) leads generally to the β-isomer in which the copper atom adds to the carbon β of the

• the coordination of the organometallic species by the sulfonyl group should control the regioselectivity of the carbometallation reaction in favor of the α-isomer. When 2 was added to an organocopper (easily prepared by the addition of one equivalent of R2MgBr to one equivalent of CuBr in Et2O at −50

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• ] However, the C2-selectivity observed in the presence of Cu(I) salts as cocatalyst, or used alone, was suspected to arise from a proton–metal exchange of the most acidic position leading to an organocopper intermediate suitable for a nucleophilic substitution reaction. Daugulis reported a first

• ]. The resulting C2-carbanion may be in equilibrium with a stabilized carbene intermediate and finally reacts with copper iodide to give the organocopper intermediate. Bellina and Rossi also noted that this last transmetalation step may be complicated by a second, well-known equilibrium of the 2

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

• Bryan Ringstrand,
• Martin Oltmanns,
• Jeffrey A. Batt,
• Aleksandra Jankowiak,
• Richard P. Denicola and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2011, 7, 386–393, doi:10.3762/bjoc.7.49

• efficient and the product is crystalline, which simplifies its purification. Another route to VII involves a two-step sequence of conjugate addition of an organocopper reagent to glutaconate diester [38] followed by reduction (Method 1C, Scheme 1). Yield of diols from this sequence are typically around 70

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• species to an alkyne (carbometalation reaction) is an extremely useful reaction for the preparation of polysubstituted stereodefined alkenyl metal derivatives. When the organometallic species involved is an organocopper reagent, the reaction is termed carbocupration. To be synthetically useful, the new

• organocopper 3 must have a reactivity different from that of 1 in order to avoid oligomerization of the carbometalated product 3 (Scheme 1) [1][2][3]. For most carbocupration reactions, a strict syn-addition prevails but the regioselectivity is usually dependent of the substitution pattern of the alkyne [4

• ]. Indeed, the presence of a donor or acceptor groups in close proximity to the acetylenic moiety can influence the regioselectivity of the addition and different isomers could be formed [5][6][7]. The most pronounced effect concerns the intermolecular addition of an organocopper to α-heterosubstituted