Iridium-Catalyzed anti-Diastereo- and Enantioselective Carbonyl (Trimethylsilyl)allylation from the Alcohol or Aldehyde Oxidation Level

Abstract

Using the ortho-cyclometallated π-allyl iridium precatalyst (R)-I derived from [Ir(cod)Cl] 2 , 4-cyano-3-nitrobenzoic acid, (R)-SEGPHOS and allyl acetate, enantioselective transfer hydrogenation of α-(trimethylsilyl)allyl acetate in the presence of aldehydes 2a-2i mediated by isopropanol delivers products of (trimethylsilyl)allylation 4a-4i in good isolated yields and with exceptional levels of anti-diastereoselectivity and enantioselectivity (90-99% ee). In the absence of isopropanol, but under otherwise identical reaction conditions, carbonyl (trimethylsilyl)allylation is achieved directly from alcohol oxidation level to furnish an equivalent set of adducts 4a-4i with roughly equivalent isolated yields and stereoselectivities. To evaluate the synthetic utility of the reaction products 4a-4i, adduct 4g was converted to the 1,4-ene-diol 5g via dioxirane mediated oxidative desilylation with allylic transposition, the allylic alcohol 6g via protodesilylation with allylic transposition, and the γ-lactam 7g via chlorosulfonyl isocyanate mediated cycloaddition.

Catalytic Enantioselective CH Functionalization of Alcohols by Redox‐Triggered Carbonyl Addition: Borrowing Hydrogen, Returning Carbon

“…In terms of scope, such cyclometalated iridium C , O ‐benzoate complexes catalyze the CC coupling of benzylic, allylic, and aliphatic primary alcohols with a remarkably diverse range of π‐allyl precursors. For example, as illustrated in the anti ‐diastereo‐ and enantioselective α‐(hydroxymethyl)allylation,20a α‐(trimethylsilyl)allylation,20b and α‐(trifluoromethyl)allylation20c of primary alcohols, reactions employing α‐substituted allylic carboxylates with monosubstituted alkenes are especially facile (Scheme ). For allylic pronucleophiles that possess higher degrees of olefin substitution (Scheme ),21 the diminished stability of the olefin π‐complex22 impedes ionization of the allylic leaving group to form the nucleophilic π‐allyliridium intermediate.…”

Formation of C–C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation

“…For example, iridium-catalyzed transfer hydrogenation of α-(trimethylsilyl)allyl acetate in the presence of aldehydes mediated by isopropanol and employing the iridium catalyst modified by ( R )-SEGPHOS [272] delivers products of (trimethylsilyl)allylation in good isolated yields and with exceptional levels of anti -diastereo and enantiocontrol [300]. In the absence of isopropanol, carbonyl (trimethylsilyl)allylation is achieved directly from the alcohol oxidation level to furnish an equivalent set of adducts (Scheme 26, top).…”

Rhodium(I) complexes with κP coordinated ω-phosphinofunctionalized alkyl phenyl sulfide, sulfoxide and sulfone ligands and their reactions with sodium bis(trimethylsilyl)amide and Ag[BF4]

“…In the case of the sulfinylfunctionalized ligands (x ¼ 1) the deprotonation of the prochiral CH 2 group creates a second chiral center; noteworthy, the formation of the respective organorhodium complexes (22b, 23b) proved to be diastereoselective. The diastereoselective synthesis of metallacycles [53e55] and their use as catalysts [56,57] have been described in literature previously. 5.…”