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Catalytic enantioselective coupling of 1,1‐disubstituted allenes and aldehydes through regiodivergent oxidative cyclization followed by stereoselective protonation or reductive elimination promoted by chiral phosphine‐Co complexes is presented. Such processes represent unprecedented and unique reaction pathways for Co catalysis that enable catalytic enantioselective generation of metallacycles with divergent regioselectivity accurately controlled by chiral ligands, affording a wide range of allylic alcohols and homoallylic alcohols that are otherwise difficult to access without the need of pre‐formation of stoichiometric amounts of alkenyl‐ and allyl‐metal reagents in up to 92 % yield, >98 : 2 regioselectivity, >98 : 2 dr and >99.5 : 0.5 er. [ABSTRACT FROM AUTHOR]

An efficient pincer‐ligand‐based cobalt‐complex‐catalyzed allene hydroboration affording Z‐allylic boronates is described. The reaction demonstrates an excellent regio‐ as well as Z‐stereoselectivity and a wide substrate scope that tolerates many functional groups. Based on solvent‐assisted electrospray ionization mass spectrometry (SAESI‐MS) studies, a rationale for the cobalt‐catalyzed hydroboration involving the highly selective insertion of an allene into the Co−H bond to form Z‐allylic cobalt intermediates is proposed. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: β‐H elimination is an intrinsic problem in transition metal‐catalyzed reactions. We describe herein an interesting ligand effect for Et2Zn acting as either ethyl provider or H provider, respectively: by applying SPhos or Gorlos‐Phos as the ligand, β‐H elimination has been successfully controlled in the corresponding Negishi coupling reaction affording different poly‐substituted allenes in good yields and excellent selectivities. SAESI‐MS (Solvent Assisted Electrospray Ionization Mass Spectrometry) has been applied to successfully capture the highly reactive organometallic intermediates, which show the different coordination behaviors of Pd with SPhos or Gorlos‐Phos as the ligand in the catalytic cycle. In addition, the different reactivities of Int 1 and Int 2 towards the formation of the final allene products have been demonstrated via SAESI‐MS/MS experiments. These MS studies visualized the whole catalytic cycle for the Negishi coupling reaction while nicely explain the observed reactivity and selectivity. [ABSTRACT FROM AUTHOR]

A simple and efficient method for the synthesis of 1,4-dihydroarenes by gold-catalyzed 6- endo cyclization of benzylic allenes has been developed. Furthermore, asymmetric hydroarylation of enantioenriched allenes has been realized to offer a practical and convergent approach to aromatic ring-fused six-membered cycles containing a chiral stereocenter such as 1,4-dihydronaphthalenes, 1,4-dihydrodibenzo[ b, d]thiophenes, and 4,7-dihydrobenzo[ b]thiophenes by applying dinuclear [(dppm)Au2Cl2] [dppm=methylenebis(diphenylphosphane)] combined with AgOTf as the catalyst to ensure the high efficiency of chirality transfer. ESI-MS has been applied to characterize some of the key reactive dinuclear gold intermediates successfully. [ABSTRACT FROM AUTHOR]

The Cu/Zn-catalyzed reaction of alkyne (I) with aldehydes (II) in the presence of (S)-α,α-diphenylprolinol affords (S)-allenes (III), which are converted into chiral 1-aryl-1,4-dihydronaphthalenes (IV). [ABSTRACT FROM AUTHOR]