Recent Advances in the Preparation of Allylboronates and Their Use in Tandem Reactions with Carbonyl Compounds

Highly Diastereo- and Enantioselective Allylboration of Aldehydes using α-Substituted Allyl/Crotyl Pinacol Boronic Esters via in Situ Generated Borinic Esters

“…Among methods for making C–C bonds, asymmetric allylboration of aldehydes is one of the most reliable and important in synthesis . Since Hoffmann’s realization that relative stereochemistry could be controlled by the double-bond geometry of crotylboronates and Brown’s discovery of highly enantioselective allylborations using pinane-derived reagents, this reaction has established strong roots in synthesis.…”

Catalyst-Enabled Stereodivergence in Photochemical Atom Transfer Radical Addition (ATRA) of α-Iodoboronic Esters to Alkynes

“…Allylic boronic acids or their esters hold a position of utmost importance in the field of organoboron chemistry, as their extensive applications in organic synthesis are widely recognized. − The unique combination of an adjacent double bond and a boryl moiety imparts them with distinct and valuable reactivities, setting them apart from conventional organoborons. This is exemplified by their key role in allylboration reactions that enable the efficient transformation of carbonyl and imine functionalities. , Remarkably, these reactions often proceed through a highly organized “closed” Zimmerman–Traxler (ZT) transition state, leading to a high degree of diastereoselectivity and the synthesis of complex 3D architectures from simple 2D fragments in a stereocontrolled manner. − The diastereospecific nature of these reactions also emphasizes the significance of employing stereodefined allylborons, as the E and Z isomers produce distinct diastereoisomeric products (Scheme A). − …”

“…a Yield determined by analysis of the crude 1 H NMR spectra using CH 2 Br 2 as an external standard. b Geometric ratio determined by1 H NMR spectroscopy from the crude product. PMP: 1,2,2,6,6pentamethylpiperidine, PC1: 4CzIPN (2,4,5,6-tetra(9H-carbazol-9yl)-1,3-dicyanobenzene), CyH: cyclohexane, PC2: Ir(ppy) 3 , PC3: entry 10), while the absence of light prevented product formation, emphasizing its fundamental role (Table1, entry 11).…”

Copper(I)-Catalyzed Enantioselective Synthesis of α-Chiral Linear or Carbocyclic (E)-(γ-Alkoxyallyl)boronates

“…Consequently, stereoselective coupling reactions constructing chiral 1,2-diol motifs with concurrent C–C bond formation between two functionalized synthetic fragments can be powerful tools for the efficient convergent synthesis of the complex polyols containing multiple stereocenters . Addition reactions of enantioenriched γ-alkoxyallyl organometallic reagents to a carbonyl compound have been employed for the construction of the stereodefined 3-ene-1,2-diol structure with a concomitant C–C bond formation, and the double bond in the product can be further utilized through a number of selective functionalization reactions. ,,, Among the γ-alkoxyallyl organometallic reagents, (γ-alkoxyallyl)­boron compounds are commonly used as versatile reagents for asymmetric synthesis because they react both reliably and predictably, exhibiting high levels of stability under atmospheric conditions and low toxicity . Following from the initial studies of Hoffmann and Wuts, the stereoselective allylation of aldehydes with (γ-alkoxyallyl)boron compounds has been used for the synthesis of polyoxygenated natural products and pharmaceuticals .…”