Cobalt-Catalyzed Allylzincations of Internal Alkynes

Abstract

Cobalt salts such as cobalt(II) chloride catalyze allylzincation reactions of 1-aryl-1-alkynes. The allylzincations proceed in a syn fashion to form 2-allyl-1-aryl-1-alkenylzinc species. Other internal alkynes such as 6-dodecyne or 2-nonyn-1-ol are much less reactive than 1-aryl-1-alkynes.

Carbozincation of Substituted 2-Alkynylamines, 1-Alkynylphosphines, 1-Alkynylphosphine Sulfides with Et2Zn in the Presence of Catalytic System of Ti(O-iPr)4 and EtMgBr

“…Our study supplements Negishi's work on Ti-Mg-catalyzed cyclozincation of α,ω-enynes with Et 2 Zn well [2]. It is known that Cu-, Ni-, Co-, and Ru-catalyzed carbozincation of alkynyl sulfoximines, alkynyl sulfones [3], 1-alkynyl sulfoxides [4], propargylic ethers [5], propargyl alcohols [6], and ynamides [7,8] is an effective tool for the synthesis of polysubstituted functionalized olefins. As regards the carbozincation of inactivated alkynes, a limited number of examples are reported in the literature.…”

“…Ni-catalyzed stereoselective carbozincation of but-1-yn-1-ylbenzene with Ph 2 Zn is known [9], as well as Co-catalyzed allylzincation of aryl alkynes [10]. As to the effective carbozincation of dialkyl substituted alkynes, only ethylzincation [6] and allylzincation [11] of dec-5-yne in the presence of stoichiometric amounts of Cp 2 ZrI 2 were described in the literature. It should be emphasized that the use of a catalytic system consisting of EtMgBr and Ti(O-iPr) 4 for 2-zincethylzincation of α,ω-enynes was first reported by Negishi [2].…”

2-Zincoethylzincation of 2-Alkynylamines and 1-Alkynylphosphines Catalyzed by Titanium(IV) Isopropoxide and Ethylmagnesium Bromide

“…Coupling between the protons at С-4 (δ = 2.38 ppm) and the С-8 carbon (δ = 141.16 ppm) in 10a points to the geminal positions of the phenyl and ethyl groups at a double-bond carbon. Comparison of the 1 Н NMR and 13 C NMR signal intensities for compounds 10a and 10′a leads to the conclusion that compound 10a is present in a 1.5-fold greater amount in the isomer mixture. Presumably, agostic interaction between the titanium atom and the ortho-hydrogen atom of the phenyl group may be one of the causes for the observed lack of regioselectivity in the transformation of aryl-substituted propargylamines 8.…”

“…12 However, CoCl 2 -catalyzed allylzincation of substituted propargyl alcohols with allylzinc bromide proceeds with a low yield giving mixtures of regio-and stereoisomers. 13 The Rh-and Co-catalyzed carbozincation of ynamides can be used for selective synthesis of multisubstituted enamides and dienamides, 14 and also 3-arylenamides. 15 The number of known catalytic carbozincation reactions of alkynylamines is modest.…”

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

“…They applied the reaction toward the synthesis of an estrogen-receptor antagonist (Scheme 37). Although the cobalt-catalyzed allylzincation reactions of dialkylacetylenes resulted in low yield, the reactions of arylacetylenes provided various tri- or tetrasubstituted styrene derivatives (Scheme 38) [119–120]. …”