Alkylations of Functionalized Organozinc Reagents with Allylic EpoxidesCatalyzedby A Cyanocuprate

Asymmetric Ring‐Opening of Epoxides and Aziridines with Carbon Nucleophiles

“…Allylic epoxides, also called vinyl oxiranes, can be considered as a special class of allylic substrates because they combine the reactivity of epoxides and that of allylic substrates, thus allowing a wide range of synthetically useful transformations 65. As dialkylzincs are hard alkyl nucleophiles, but usually too weak to react with these conjugate systems, it was tempting to consider the possibility of generating a cuprate in situ by a transmetalation reaction leading to more reactive and selective species 66. To our delight, we found a remarkable ligand‐accelerated catalysis effect in the presence of a catalytic amount of copper complexes with Binol‐based phosphoramidites such as 13 (Scheme ) 67…”

Regioselective and Divergent Opening of Vinyl Epoxides with Alkyne Nucleophiles

“…In contrast with the S N 2 addition reactions, the chemoselectivity is not influenced by the electronic properties of the aromatic substituent. Nevertheless, to our delight, addition of alanes 15c and 15d proceeded with complete S N 2Ј regioselectivity (Entries [3][4][5][6]8).…”

“…Unfortunately, no general trend could be observed in the E:Z selectivity of the conjugate additions to trans-vinyl epoxides 2a-e (Entries [1][2][3][4][5][6]8). We propose that the reaction proceeds by precomplexation of the alkynylalane to the epoxide, followed by intramolecular delivery of the alkyne nucleophile (Scheme 2).…”

“…Conjugate additions of carbon nucleophiles to vinyl epoxides have been extensively studied and can be accomplished by Pd-catalyzed allylic alkylations with soft, stabilized nucleophiles, [2] organocopper reagents, [3] or copper-catalyzed additions of organomagnesium [4] or organozinc compounds. [5,6] On the other hand, regioselective S N 2 displacements can be achieved through the use of alkyllithiums in the presence of BF 3 ·OEt 2 , [7] Grignard reagents, [8] or trialkylzincates and aluminates, [9] although regioisomeric mixtures are usually obtained. A drawback with these methods is that different techniques have to be used for regioselective S N 2 and S N 2Ј additions.…”

Transmetalation Reactions Producing Organocopper Reagents

“…Use of the chiral ferrocenylamine 104 as a catalyst makes enables asymmetric allylation of diorganozinc reagents to be effected with allylic chlorides (Scheme 2.36) [78]. Related electrophiles such as propargylic bromides [79] and unsaturated epoxides [80] also undergo S N 2 0 -substitution reactions (Scheme 2.37). …”