2.01 Allylborons

Enantiospecific Synthesis of ortho-Substituted Benzylic Boronic Esters by a 1,2-Metalate Rearrangement/1,3-Borotropic Shift Sequence

“…For example, allylboration of benzaldehyde or ethyl glyoxalate afforded the corresponding alcohols 5 and 6 with excellent diastereo- and enantiocontrol (dr > 20:1, er = 95:5 and 91:9, respectively). 17 Similarly to benzylic boronic esters ( Scheme 6 a), the intermediate prepared from allylBpin underwent an enantiospecific Cope rearrangement to give 7 with 97:3 er. That the Cope rearrangement is significantly more facile than the 1,3 borotropic shift was confirmed through computation (see SI for details).…”

Copper-Mediated SN2′ Allyl–Alkyl and Allyl–Boryl Couplings of Vinyl Cyclic Carbonates

“…For the sake of comparison, the copper­(I)-catalyzed S N 2′ allylic borylation of the same allylic cyclic carbonates with B 2 pin 2 2 has also been studied, and control over the stereoselectivity of the allylic borylated product was explored since both E to Z isomers can be formed. Stereoselective synthesis of allylboronates with a hydroxyl terminus would potentially provide an unprecedented route toward functionalized allylboronates …”

Mechanistic Studies of the TRIP-Catalyzed Allylation with Organozinc Reagents

“…Regarding asymmetric synthesis, allylation reactions have a pronounced foundation and are an indispensable methodology when it comes to the creation of chiral molecules. 5 − 10 One of these examples is the asymmetric preparation of dibenzylbutyrolactones, which proceeds via the asymmetric allylation of an aldehyde precursor with an organozinc reagent. 11 , 12 The catalyst, namely, 3,3-bis(2,4,6-triisopropylphenyl)-1,1-binaphthyl-2,2-diyl hydrogenphosphate (TRIP, 2 ) 13 shows high stereoinduction on the process and delivers a natural product precursor with an enantiomeric excess as high as 98%.…”

“…Computational efforts have become a frequent tool in the elucidation of mechanistic scenarios and understanding the course of chemical reactions. − They allow the evaluation of different events by the comparison of their energetic profiles and deliver useful information to understand and improve the chemistry behind the process of interest. − Especially in combination with asymmetric synthesis, density functional theory (DFT) calculations have facilitated the finding of asymmetric induction and have delivered or confirmed the accepted mechanistic concept of activation and stereopreference. Regarding asymmetric synthesis, allylation reactions have a pronounced foundation and are an indispensable methodology when it comes to the creation of chiral molecules. − One of these examples is the asymmetric preparation of dibenzylbutyrolactones, which proceeds via the asymmetric allylation of an aldehyde precursor with an organozinc reagent. , The catalyst, namely, 3,3-bis­(2,4,6-triisopropylphenyl)-1,1-binaphthyl-2,2-diyl hydrogenphosphate (TRIP, 2 )shows high stereoinduction on the process and delivers a natural product precursor with an enantiomeric excess as high as 98%. Important to note is the fact that the reaction has a boron congener, using allyl boronate reagents and the same catalyst .…”