Copper(I) tert-Butoxide-Promoted 1,4 C^sp2-to-O Silyl Migration:  Stereospecific Allylation of (Z)-γ-Trimethylsilyl Allylic Alcohols

Abstract

[reaction--see text] The cyclic silyl ethers, 2,2-dimethyl-1-oxa-2-sila-3-cyclopentenes, were produced by the treatment of (Z)-gamma-trimethylsilyl allylic alcohols with a catalytic or stoichiometric amount of lithium tert-butoxide. On the other hand, successive treatment of the alcohols with copper(I) tert-butoxide and allylic halides followed by the tetrabutylammmonium fluoride assisted hydrolysis produced the allylation products, 2,5-alkadien-1-ols, with complete retention of configuration of the double bond.

Synthesis and Reactivity of Functionalized Arylcopper Compounds by Transmetalation of Organosilanes

“…The intermediacy of organocopper species has been inferred in reactions of highly strained silanes 7 and of those activated by intramolecular alkoxides. 8 A few reports demonstrating copper catalysts for organosilane dimerization, 9 for coupling of alkynylsilanes, 10 or for nucleophilic addition of organosilanes have appeared, 11 primarily with more easily transferable allylsilane nucleophiles. 12,13 The intermediacy of organocopper species can be inferred in these reactions on the basis of kinetics, NMR, and enantioselection observations, 11,14 but it can be difficult to distinguish reactivity of an organocopper intermediate from that from a fluoride-activated silicate.…”

Copper(I)‐Catalyzed Alkylation of Aryl‐ and Alkenylsilanes Activated by Intramolecular Coordination of an Alkoxide

“…10 The 1,4‐silyl migration proceeds by formation of the five‐membered cyclic silicates 3 , which undergo the transmetallation to copper(I) to form the organocopper species 4 by the “endo”cyclic SiC bond cleavage in association with the silyl migration [Scheme , Eq. (2)] 9a–d. The organocopper species 4 reacts with alkyl, allylic, and benzylic halides [C(sp 3 )X electrophiles] to give the alkylation products 5 in good yields.…”

C(sp2)−Si Bond Functionalization through Intramolecular Activation by Alkoxides

“…In 2001, the Takeda group developed a strategy for the stereoselective allylation of ( Z )‐γ‐trimethylsilyl allylic alcohols 10 [26] . Successive treatment with copper(I) tert ‐butoxide and allyl halides in DMF, followed by the TBAF‐assisted hydrolysis, yielded dienyl alcohols 11 with complete retention of the configuration of the double bond (Scheme 5).…”