Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• addition is paramount, this method is currently limited to the use of a large excess of olefins; however, activated alkenes could circumvent this requirement. In 2016, the Deng group studied a novel double carbomagnesiation of unsymmetrical internal alkynes 31 with alkyl Grignard reagents 32 producing 1,3

• -dienylmagnesium reagents 33 with high regio- and stereoselectivity (Scheme 6) [68]. A major problem with the carbomagnesiation of internal alkynes bearing no heteroatoms is the relatively harsh conditions required producing poor selectivity in some cases [69][70]. The strong σ-donating nature of the IEt2Me2NHC

• Echeverria demonstrated a mechanistically distinct protocol for the synthesis of 1,3-dienes 36 (Scheme 7) [72]. Compared to previous Fe-catalyzed carbomagnesiation reactions (Scheme 6) where carbometallation occurs in a concerted syn-manner this protocol, instead, is initiated by the oxidative cyclization of

Diastereo- and enantioselective preparation of cyclopropanol derivatives

• Marwan Simaan and
• Ilan Marek

Beilstein J. Org. Chem. 2019, 15, 752–760, doi:10.3762/bjoc.15.71

• , followed by a subsequent trapping of the resulting cyclopropylmetal species with an electrophilic source of oxygen (oxenoid) afforded various tetrasubstituted cyclopropanol derivatives in high diastereo- and enantiomeric ratios. Similarly, the enantioselective copper-catalyzed carbomagnesiation/oxidation

• polysubstituted enantioenriched cyclopropanols. As reported, the copper-catalyzed diastereo- and enantioselective carbomagnesiation reaction of cyclopropenes 6 was easily achieved in the presence of (R,S)-Josiphos (2.2 mol %, Scheme 7). Having in hand, diastereoisomerically pure and enantiomerically enriched

• enantiomeric ratios (er up to 99:1, Scheme 7). Following the same concept of copper-catalyzed diastereo- and enantioselective carbomagnesiation reaction of cyclopropenes 6 followed now by a selective electrophilic amination reaction, a powerful entry to cyclopropylamines as single diastereoisomer and in

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

• species. To improve the chemical yield of this transformation, we considered the copper-catalyzed carbomagnesiation reaction. However, such catalytic reaction requires a transmetallation reaction of the intermediate vinylcopper into vinylmagnesium halide, and due to the intramolecular chelation, it is

• usually performed at higher temperature. Thus, a thermally more stable organocopper species [formed from copper(I) bromide–dimethylsulfide complex (CuBr·Me2S)], was used for this copper-catalyzed carbomagnesiation reaction. We were pleased to see that the reaction is very efficient for the addition of

• a α/β ratio of 18:82. When N-alkynylamide 4 was treated under our copper-catalyzed carbomagnesiation conditions (conditions B), enamides 6 were similarly obtained as a pure α-isomer. Although this transformation requires higher temperature, yields are usually better than in reactions with the

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• Kei Murakami Hideki Yorimitsu Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan Japan Science and Technology Agency, Department of Research Projects (ACT-C), Tokyo 102-0076, Japan 10.3762/bjoc.9.34 Abstract Carbomagnesiation and carbozincation

• involving wide varieties of substrates and reagents. Recent advances of transition-metal-catalyzed carbomagnesiation and carbozincation reactions are reviewed in this article. The contents are separated into five sections: carbomagnesiation and carbozincation of (1) alkynes bearing an electron-withdrawing

• group; (2) alkynes bearing a directing group; (3) strained cyclopropenes; (4) unactivated alkynes or alkenes; and (5) substrates that have two carbon–carbon unsaturated bonds (allenes, dienes, enynes, or diynes). Keywords: alkene; alkyne; carbomagnesiation; carbometalation; carbozincation; transition

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

• 80/20, Scheme 7). Copper-catalyzed carbomagnesiation could even further increase the efficiency of these reactions. Thus, when ethynyl carbamate 12a was added to a stoichiometric amount of alkylmagnesium halide in Et2O in the presence of 10 mol % CuI, the corresponding (E)-substituted alkene was

• obtained in 70% isolated yield after hydrolysis [9]. The addition of a typical electrophile to vinylmagnesium halide species such as aldehydes, is therefore now possible. Interestingly, this copper-catalyzed carbomagnesiation reaction proceeds at slightly higher temperatures than the stoichiometric process

• (CuI leads to roughly 20% less). Copper-catalyzed carbomagnesiation leads to the same stereochemistry although this transformation requires a slightly higher temperature (−30 °C to rt). Et2O is the solvent of choice for this transformation since THF leads to the branched isomer as the major product