Exploration of an epoxidation–ring-opening strategy for the synthesis of lyconadin A and discovery of an unexpected Payne rearrangement

• Brad M. Loertscher,
• Yu Zhang and
• Steven L. Castle

Beilstein J. Org. Chem. 2013, 9, 1179–1184, doi:10.3762/bjoc.9.132

• stereoselective sequence involving a Myers alkylation and a Shi epoxidation. Ring-opening of this epoxide with a vinylcopper complex afforded alcohol 26 instead of the expected product 27. An unusual Lewis acid promoted Payne rearrangement of an α-trityloxy epoxide is proposed to account for this outcome

• in Scheme 6. Coordination of a Lewis acid (likely a copper or magnesium species) to the trityl ether moiety of 25 could promote migration of the trityl group [31][32] to the epoxide, generating intermediate A. Payne rearrangement of A would then furnish epoxide B. Finally, attack of the vinylcopper

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

• carbocupration reactions of heterosubstituted alkynes allow the regio- and stereoselective formation of vinyl organometallic species. N-Alkynylamides (ynamides) are particularly useful substrates for the highly regioselective carbocupration reaction, as they lead to the stereodefined formation of vinylcopper

• ), but for groups that are known to be sluggish in carbocupration reaction, such as the introduction of a Me group (Table 1, entry 2), yield is significantly lower. The presence of the vinylcopper was proved by the reaction with allyl bromide as a classical electrophile used in organocopper chemistry to

• 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

Highly stereocontrolled synthesis of trans-enediynes via carbocupration of fluoroalkylated diynes

• Tsutomu Konno,
• Misato Kishi and
• Takashi Ishihara

Beilstein J. Org. Chem. 2012, 8, 2207–2213, doi:10.3762/bjoc.8.249

• regioselectivity was observed [32][33][34][35].) Accordingly, a transfer of the R2 group on CuIII to the olefinic carbon distal to a CF3 group may take place preferably, with vinylcopper intermediate Int-E, not Int-F, being produced exclusively. As a result, vinyl iodide 13 can be given in a highly regio- and

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

• change the stereochemical outcome of the reaction. Representative examples are given in this mini-review. Keywords: alkynes; carbocupration; enamides; regioselectivity; stereoselectivity; syn-addition; vinylcopper; ynamides; ynol ether; Review The addition of a carbon-metal bond of an organometallic

• α-sulfinyl vinylcopper and zinc intermediates, 36 and 37 respectively, retain their geometry at room temperature is in sharp contrast to α-sulfinyl vinyllithium- or magnesium species that isomerize to the thermodynamically more stable geometric isomer at low temperature. When an enantiomerically