Stereoselective Synthesis of 1,4-Diols by a Tandem Allylboration–Allenylboration Sequence

Abstract

The reaction of mono- and dialdehydes with bis-borodienes (incorporating an allylboronate unit) has been studied. It was found that the initial allylboration reaction results in an allenylboronate, which has two stereogenic units: one of them has axial chirality and the other one is a stereogenic carbon center. This reaction proceeds with high diastereoselectivity. The allenylboronate formed in the allylboration reacts with an additional aldehyde with fair to high stereoselectivity depending on the aldehyde substrate. Aromatic dialdehydes react with bis-boro-butadienes creating three new stereocenters with usually high diastereoselectivity.

Recent Advances in Boron‐Substituted 1,3‐Dienes Chemistry: Synthesis and Application

“…In 2015, Szabo et al [187] reported the reaction of mono-and dialdehydes 431 a or 431 b with bis-boronatedienes 430 (incor-porating an allylboronate unit) as as tereoselective synthesis of 1,4-diols 434 by at andem allylboration-allenylboration sequence(Scheme 114).…”

Copper‐Mediated Dichotomic Borylation of Alkyne Carbonates: Stereoselective Access to (E)‐1,2‐Diborylated 1,3‐Dienes versus Traceless Monoborylation Affording α‐Hydroxyallenes

“…The scope of this stereoselective diborylation process (Scheme 2) was further investigated using a more ample set of alkynyl cyclic carbonate precursors ( S1 – S16 : for their synthesis, see the Supporting Information) [9] . Diborylated compounds 1 – 12 were produced with a high degree of stereocontrol, appreciable yields and reasonable skeletal variation useful in post‐synthetic operations [11b] . Products 13 – 16 , however, were isolated in low yields and with substantially lower levels of stereoinduction which is ascribed to the increasing steric impediment exerted by the R 2 and R 3 substituents of the cyclic carbonate precursor.…”

Catalytic Borylative Opening of Propargyl Cyclopropane, Epoxide, Aziridine, and Oxetane Substrates: Ligand Controlled Synthesis of Allenyl Boronates and Alkenyl Diboronates

“…In the presence of PCy 3 alkenyl diboronates form with high regio‐ and stereoselectivities, while with the bulky P(1‐nap) 3 ligand the product is the allenyl boronate. This process provides a large variety of allyl/alkenyl‐ and allenyl boronates, which are useful reagents in functionalization of carbonyl compounds for stereoselective synthesis of homoallyl and homopropargylic alcohols,,, and useful precursors for allenyl derivatives by Suzuki–Miyaura coupling …”