Platinum-Catalyzed Silaborative Coupling of 1,3-Dienes to Aldehydes: Regio- and Stereoselective Allylation with Dienes through Allylic Platinum Intermediates

Regio-controllable Cobalt-Catalyzed Sequential Hydrosilylation/Hydroboration of Arylacetylenes

Regiodivergent addition reactions provide straightforward and atom-economic approaches to access different regioisomers. However, the regio-chemistry control to access all the possible results is still challenging especially for the reaction involving multiple addition steps. Herein, we reported regio-controllable cobalt-catalyzed sequential hydrosilylation/hydroboration of arylacetylenes, delivering all the possible regio-outcomes with high regioselectivities (up to >20/1 rr for all the cases). Each regioisomer of value-added silylboronates could be efficiently and regioselectively obtained from the same materials. The adjustment of the ligands of cobalt catalysts combined with dual catalysis relay strategy is the key to achieve regio-chemistry control. This regio-controllable research might inspire the exploration of the diversity-oriented synthesis that involves multiple additions and provide full sets of regioisomers of other synthetic useful molecules.

[n]Dendralenes as a Platform for Selective Catalysis: Ligand-Controlled Cu-Catalyzed Chemo-, Regio-, and Enantioselective Borylations

We report the development of two complementary methods for the Cu-catalyzed anti-Markovnikov borylation of one specific olefin in 2-substituted [n]dendralenes (n = 3-6). The first protocol operates with a bisphosphine ligand and occurs with high regio- and chemoselectivity for the terminal double bond, independently of the number of cross-conjugated alkenes. We show that the use of a chiral phosphanamine ligand enables the highly chemo-, regio-, and enantioselective borylation of the alkene cross-conjugated with the terminal olefin in [n]dendralenes.

α-Silicon effect assisted Curtin-Hammett allylation using allylcopper reagents derived from 1,3-dienylsilanes

Cu-catalyzed stereoselective synthesis of (E)-δ-silyl-anti-homoallylic alcohols from 1,3-dienylsilane was developed. Mechanistic studies revealed that the borocupration of dienylsilane proceeded through a 1,2-addition pathway to give an allylcopper intermediate with Cu distal to the silyl group. However, the subsequent aldehyde allylation proceeded via Curtin-Hammett control to give (E)-δ-silyl-anti-homoallylic alcohols with high diastereoselectivities. This method was applied to the synthesis of the C1-9 fragment of a polyketide natural product, mycinolide IV.

Intermolecular Metal-Catalyzed Reductive Coupling of Dienes, Allenes, and Enynes with Carbonyl Compounds and Imines

Metal-catalyzed reductive coupling has emerged as an alternative to the use of stoichiometric organometallic reagents in an increasingly diverse range of carbonyl and imine additions. In this review, the use of diene, allene, and enyne pronucleophiles in intermolecular carbonyl and imine reductive couplings are surveyed, along with related hydrogen autotransfer processes.

Catalytic bismetallative multicomponent coupling reactions: scope, applications, and mechanisms

Catalytic reactions have played an indispensable role in organic chemistry for the last several decades. In particular, catalytic multicomponent reactions have attracted significant attention due to their efficiency and expediency towards complex molecule synthesis. The presence of bismetallic reagents (e.g. B-B, Si-Si, B-Si, Si-Sn, etc.) in this process renders the products enriched with various functional groups and multiple stereocenters. For this reason, catalytic bismetallative coupling is considered an effective method to generate the functional and stereochemical complexity of simple hydrocarbon substrates. This review highlights key developments of transition-metal catalyzed bismetallative reactions involving multiple π components. Specifically, it will highlight the scope, synthetic applications, and proposed mechanistic pathways of this process.

Potassium tert-butoxide-mediated regioselective silaboration of aromatic alkenes

The regio- and diastereoselective silaboration of aromatic alkenes with a silylboron compound proceeds in the presence of a catalytic amount of potassium tert-butoxide, providing a complementary method to the corresponding transition metal-catalyzed reactions.

Platinum-catalyzed diastereoselective intramolecular coupling of allyl halides and hydrazones

Nucleophilic allyl platinum addition to hydrazones under platinum-catalyzed conditions was studied. To generate nucleophilic allyl platinum complexes, allyl halides were employed with platinum complexes, SnCl(2), and H(2). The allyl platinum(IV) intermediates reacted with the hydrazone to give the corresponding cyclic amine derivatives in good yield and with excellent diastereoselectivity. The cis selectivity of N-tethered substrates was attributed to a tight interaction of allyl platinum species with the hydrazone, on the basis of the results of solvent screening and acid/base addition experiments.

Palladium-catalyzed silylene-1,3-diene [4 + 1] cycloaddition with use of (aminosilyl)boronic esters as synthetic equivalents of silylene

Silylboronic esters bearing a dialkylamino group on the silicon atoms reacted with 1,3-dienes in the presence of a palladium catalyst to give silacyclopent-3-enes (i.e., 2,5-dihydrosiloles) in high yields via efficient silylene transfer from the silylboronic ester to the 1,3-dienes. The [4 + 1] cycloaddition was applicable to the parent 1,3-butadiene and various mono-, di-, and trisubstituted 1,3-dienes having silyloxy, cyano, and ester groups. Stereospecific ring formation took place in the reaction with either stereoisomer of 5,7-dodecadiene: the (E,E)-diene gave the cis product, whereas selective formation of the trans product was observed in the reaction of the isomeric (E,Z)-diene. The [4 + 1] cycloaddition followed by dehydrogenation with DDQ or chloranil afforded 2,4- and 2,5-diarylsiloles.

Platinum-catalyzed tandem diboration/asymmetric allylboration: access to nonracemic functionalized 1,3-diols

[reaction: see text] A single-pot tandem catalytic diene diboration/carbonyl allylation reaction is described that uses a commercially available chiral diboron reagent. The chirality of the intermediate diboration adduct is transferred to the product in the carbonyl allylation reaction, thereby providing access to enantioenriched chiral products. Notably, the reaction allows for construction of a quaternary stereocenter and furnishes a synthetically versatile C-B bond in the reaction product.