Catalytic Enantioselective Alkylations with Allylic Alcohols

Abstract

Allylic alcohols have recently risen to prominence as a valuable synthetic alternative to classic activated alkylating agents in asymmetric catalysis. The intrinsic drawbacks that limited their employment in catalytic enantioselective transformations, until recently, have been efficiently addressed providing elegant solutions. This short review intends to summarize the most salient and recent outcomes in this emerging research area, highlighting the scope and limitations of the most selective catalytic methodologies.

Asymmetric Allylic Alkylation of β‐Ketoesters with Allylic Alcohols by a Nickel/Diphosphine Catalyst

“…[3,4] Because alcohols are poor electrophilic species,h owever,h igh catalyst loading, high reaction temperatures,a nd/or external activators of hydroxy groups are required. [5] In this context, some asymmetric alkylation reactions using allylic alcohols have been reported: b-Diesters were used as nucleophiles in an AAA reaction of allylic alcohols to give allylated products having ac hiral center on an allylic moiety (Scheme 1a); [6] 3-subsituted indoles were used in aF riedel-Crafts-type alkylation with allylic alcohols as the alkylating agents (Scheme 1b); [7] abranched aldehydes and ketones acted as nucleophiles in palladium-and iridium-catalyzed enantioselective allylation assisted by primary or secondary amines (Scheme 1c); [8] Gong and Jiang independently developed an AAA reaction of pyrazol-5-ones and azlactone with allylic alcohols using palladium complexes and chiral phosphoric acids (Scheme 1d); [9] and alkenyl trifluoroborates were also used for asymmetric allylic alkenylation in the presence of iridium/ phosphoramidite complexes (Scheme 1e). [10] Despite these advances,however, reactions in which precious metals can be replaced by inexpensive and earth-abundant metals are in high demand.We previously demonstrated that nickel complexes bearing diphosphine ligands exhibit catalytic activity for direct amination of allylic alcohols,i nw hich tetrabutylammonium acetate has remarkable additive effects.…”

Synthesis and Applications in Catalysis of Metal Complexes with Chelating Phosphinosulfonate Ligands

“…Following the same trend, Nozaki demonstrated that the formation of the sixmembered palladium(II) complex occurred similarly from the imidazolium sulfonate ligand precursor. 87,88 The (pentamethylcyclopentadienyl)(allyl)ruthenium(IV) complex containing the phosphinosulfonate chelate 2a was efficiently applied in the regioselective allylation of carbonucleophiles and phenols with unsymmetrical allylic chlorides to give branched products. 26 However, reports dealing with the formation of seven-membered chelates are scarce due to the relative instability of these systems.…”

Enantioselective Dearomatization of Naphthol Derivatives with Allylic Alcohols by Cooperative Iridium and Brønsted Acid Catalysis

“…Having identified the optimized reaction conditions of the enantioselective allylic dearomatization reaction, we explored the substrate scope of the reaction in the presence of the (R)-L1/Ir I complex and rac-PA7,a ss ummarized in Table 3. Firstly,various allylic alcohols (1)w ere reacted with 2a to afford the linear products with excellent chemo-and enantioselectivities (entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Awide range of aromatic groups bearing electron-rich and electron-deficient substituents on either the ortho-, meta-, or para-position of the allyl alcohols 1 were all tolerated and gave rise to the products in moderate to good yields (51-87 %) with good to excellent enantioselectivities (86-> 99 % ee).…”