- Copper-Catalyzed Tandem Hydrocupration and Diastereo- and Enantioselective Borylalkyl Addition to Aldehydes
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We report the copper-catalyzed stereoselective addition of in situ generated chiral boron-α-alkyl intermediates to various aldehydes including α,β-unsaturated aldehydes under mild conditions. This tandem and multicomponent method facilitated the synthesis of enantiomerically enriched 1,2-hydroxyboronates bearing contiguous stereocenters in good yield with high diastereo- and enantioselectivity up to a ratio greater than 98:2. In particular, α,β-unsaturated aldehydes were successfully used as electrophiles in Cu?H catalysis through 1,2-addition without significant reduction. The resulting 1,2-hydroxyboronates were used in various transformations.
- Jang, Won Jun,Yun, Jaesook
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supporting information
p. 12116 - 12120
(2018/09/11)
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- Aluminum Hydride Catalyzed Hydroboration of Alkynes
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An aluminum-catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL-H or bench-stable Et3Al?DABCO as the catalyst and H-Bpin as both the boron reagent and stoichiometric hydride source has been developed. Mechanistic studies revealed a unique mode of reactivity in which the reaction is proposed to proceed through hydroalumination and σ-bond metathesis between the resultant alkenyl aluminum species and HBpin, which acts to drive turnover of the catalytic cycle.
- Bismuto, Alessandro,Thomas, Stephen P.,Cowley, Michael J.
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supporting information
p. 15356 - 15359
(2016/12/06)
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- Catalyst-controlled selectivity in the C-H borylation of methane and ethane
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The C-H bonds of methane are generally more kinetically inert than those of other hydrocarbons, reaction solvents, and methane functionalization products.Thus, developing strategies to achieve selective functionalization of CH4 remains a major
- Cook, Amanda K.,Schimler, Sydonie D.,Matzger, Adam J.,Sanford, Melanie S.
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p. 1421 - 1424
(2016/04/05)
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- σ-borane and dihydroborate complexes of ruthenium
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Room temperature reaction of the bis(dihydrogen) complex RuH2(H2)2(PCy3)2 (1) with excess pinacol borane (HBpin) generates the novel complex RuH[(μ-H)2Bpin](σ-HBpin)(PCy3)2 (2) by loss of dihydrogen. Complex 2 was characterized spectroscopically and by X-ray crystallography. It contains two pinacolborane moieties coordinated in a different fashion, one as a dihydroborate (B-H distances : 1.58(3) and 1.47(3) A) and the other as a σ-borane (B-H distance: 1.35(3) A). In addition, reaction of 1 with one equiv of HBpin yields total conversion to a new complex tentatively formulated as RuH[(μ-H)2Bpin](H2)(PCy3)2 (3) on the basis of NMR data. In the presence of excess HBpin, 3 is converted to 2. Furthermore, under an atmosphere of dihydrogen, a C7D8 solution of 2 rapidly converts to 3 and finally regenerates 1 over a much longer period. Thus, complex 3 is an intermediate in the formation of 2 from 1. In these processes the borane is eliminated as HBpin later hydrolyzed to BpinOBpin. Selective hydroboration of ethylene (3 bar) into C2H5Bpin is achieved using 1 or 2 as catalyst precursors in toluene, whereas in THF, competitive formation of the vinylborane C2H3Bpin (56% under 20 bar of C2H4) can be favored. Copyright
- Montiel-Palma, Virginia,Lumbierres, Maria,Donnadieu, Bruno,Sabo-Etienne, Slyviane,Chaudret, Bruno
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p. 5624 - 5625
(2007/10/03)
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