Intermolekulare Bildung zweier C‐C‐Bindungen an Olefinen mittels Bor‐basierter Staffelstrategien

Abstract

In der richtigen Staffelung an Olefine: Vinylboronate ermöglichen die gestaffelte Addition nucleophiler und elektrophiler oder nucleophiler und Radikal‐erzeugender Kohlenstoffreagentien an die Doppelbindung unter Erhaltung der wertvollen Boronatgruppe. Schlüssel zum Erfolg dieser schwierigen Strategie zur zweifachen C‐C‐Kupplung sind die Verlagerung der nucleophilen Addition zum B‐Atom und eine 1,2‐Metallat‐Umlagerung, die den Substituenten danach zum C‐Atom überträgt.

Radical‐Induced 1,2‐Migrations of Boron Ate Complexes

“…Following Murakami's studies on alkynyltrialkyl boron ates, Morken and co‐workers established in 2015 the use of transition metal complexes to activate alkenyl boron ate complexes in conjunctive cross‐couplings . Recently, two complementary radical approaches have been developed for both classes, 1,2‐migrations to sp 2 and sp 3 carbon centers . In the first approach, the 1,2‐boron to carbon migration is induced by an initial radical addition to the β‐position of a vinyl boron ate complex (Scheme c).…”

Enantioselective Construction of Tertiary Boronic Esters by Conjunctive Cross‐Coupling

“…(1)],a llylic borylation [4] [Eq. (3)] have facilitated the construction of tertiary boronic esters from appropriately functionalized precursor substrates.I nt his report, we describe the utility of catalytic conjunctive crosscoupling [6][7][8] as ac omplimentary means to establish highly hindered tertiary boronic esters in an efficient and enantioselective fashion (Scheme 1). (3)] have facilitated the construction of tertiary boronic esters from appropriately functionalized precursor substrates.I nt his report, we describe the utility of catalytic conjunctive crosscoupling [6][7][8] as ac omplimentary means to establish highly hindered tertiary boronic esters in an efficient and enantioselective fashion (Scheme 1).…”

“…(2)],a nd directed hydroboration [5] [Eq. (3)] have facilitated the construction of tertiary boronic esters from appropriately functionalized precursor substrates.I nt his report, we describe the utility of catalytic conjunctive crosscoupling [6][7][8] as ac omplimentary means to establish highly hindered tertiary boronic esters in an efficient and enantioselective fashion (Scheme 1).…”

“…To ensure complete reaction, each example was allowed to react for 15 ha t4 08 8C; the tertiary boronic ester products were generally isolated in good yield and selectivity.Using this procedure,aseries of substrates was examined and it was found that ab road array of migrating groups and electrophiles could be engaged in the reaction. As the data in Table 2s uggests,i na ddition to an n-butyl migrating group,h ighly hindered substituents (i.e., R M = tert-butyl;p roduct 5, 21-24)a re competent migrating groups as are aromatic groups (6)(7)(8)(11)(12)(13). Of note,o ther asubstituted boronic esters can be employed (10-13)a sc an av ariety of aryl, alkenyl, and heterocyclic electrophiles.…”