Element−Element Additions to Unsaturated Carbon−Carbon Bonds Catalyzed by Transition Metal Complexes

Asymmetric diboration of terminal alkenes with a rhodium catalyst and subsequent oxidation: enantioselective synthesis of optically active 1,2-diols

Pin it down: A highly enantioselective diboration of terminal alkenes with chiral 1 and bis(pinacolato)diboron (B2 pin2 ) was realized. Subsequent oxidation of the diboron adducts with sodium peroxoborate readily gave the corresponding optically active 1,2-diols in high yields and high enantioselectivities.

Diboran(4)yl platinum(II) complexes

The platinum diboran(4)yl complexes 1-3 have been prepared by the selective oxidative addition of one B-Hal bond in aryl-substituted diboranes(4) Hal2B2Ar2 (Hal = Cl, Ar = mes, dur; Hal = I, Ar = mes). Because of the electron deficiency of the remote B2 atom, all species show a rare dative Pt-B bonding interaction, whose magnitude is strongly dependent on the nature of the halide substituent.

Catalytic enantioselective one-pot aminoborylation of aldehydes: a strategy for construction of nonracemic α-amino boronates

We report a strategy for the conversion of aldehydes to enantiomerically enriched α-amino boronates through the intermediacy of in situ-generated silylimines. This transformation is brought about by Pt-catalyzed asymmetric addition of B2(pin)2 across the imine double bond. An attractive feature of the intermediate diboration adduct is that it can be acylated directly and provides convenient access to important N-acyl α-amino boronic ester derivatives.

A catalytic enantioselective tandem allylation strategy for rapid terpene construction: application to the synthesis of pumilaside aglycon

Catalytic enantioselective 1,2-diboration of 1,3-dienes followed by cascade allylborations with dicarbonyls provides rapid entry into carbocyclic reaction products. The stereochemical course of this reaction was studied along with its application in the synthesis of pumilaside aglycon.

Evidence for a strong trans influence of the diboran(4)yl ligand

Diboran(4)yl Pt(II) complexes: Selective oxidative addition of one B-I bond in B(2)(NMe(2))(2)I(2) to [Pt(PiPr(3))(2)] affords a trans-diboran(4)yl platinum(II) complex (see scheme; Ar(F) = 3,5-(CF(3))(2)C(6)H(3)). Comparison of its Pt-I bond lengths and the Pt-Br bond lengths of its bromine analogue with related species served to evaluate the trans influence of the ligand. The trans influence enabled facile halide abstraction to generate T-shaped 14-electron diboran(4)yl platinum(II) complexes.

Cu(II)-catalyzed synthesis of naphthalene-1,3-diamine derivatives from haloalkynes and amines

An efficient procedure for the preparation of naphthalene-1,3-diamine derivatives by copper-catalyzed haloalkynes with amines has been reported. The reaction was supposed to proceed through a coupling reaction followed by the dimerization of ynamines.

Disclosing the structure/activity correlation in trivalent boron-containing compounds: a tendency map

Most trivalent boron reagents are electrophiles owing to the vacancy for two electrons to fill the outer orbital of boron; however, interestingly, trivalent boron compounds can change their electrophilic character to a nucleophilic character by only changing the nature of the substituents on the boron atoms. With the help of computational tools, we have analyzed the structural- and electronic properties of boryl fragments that were either bonded to main-group metals or coordinated to transition-metals/rare-earth-metals and we have designed a map that might help to identify certain trends. This trend map will be useful for selecting an appropriate trivalent boron compound, depending on the sought reactivity.

Beyond benzyl grignards: facile generation of benzyl carbanions from styrenes

Benzylic functionalization is a convenient approach towards the conversion of readily available aromatic hydrocarbon feedstocks into more useful molecules. However, the formation of carbanionic benzyl species from benzyl halides or similar precursors is far from trivial. An alternative approach is the direct reaction of a styrene with a suitable coupling partner, but these reactions often involve the use of precious-metal transition-metal catalysts. Herein, we report the facile and convenient generation of reactive benzyl anionic species from styrenes. A Cu(I)-catalyzed Markovnikov hydroboration of the styrenic double bond by using a bulky pinacol borane source is followed by treatment with KOtBu to facilitate a sterically induced cleavage of the C-B bond to produce a benzylic carbanion. Quenching this intermediate with a variety of electrophiles, including CO(2), CS(2), isocyanates, and isothiocyanates, promotes C-C bond formation at the benzylic carbon atom. The utility of this methodology was demonstrated in a three-step, two-pot synthesis of the nonsteroidal anti-inflammatory drug (±)-flurbiprofen.

Copper-catalyzed double borylation of silylacetylenes: highly regio- and stereoselective synthesis of syn-vicinal diboronates

Phosphite-copper(I) complexes efficiently catalyzed the double borylation of internal silylated alkynes to provide vicinal diboronates with excellent regio- and stereoselectivity. The copper-catalyzed reaction between bis(pinacolato)diboron (B2pin2) and aryl-substituted silylacetylenes in the presence of MeOH resulted in double syn addition of the pinacolboronate moiety (Bpin) and H across the triple bond with complete selectivity. While the double borylation was highly efficient for aryl-substituted alkynylsilanes and silylacetylene, only monoborylation took place with alkyl-substituted alkynylsilanes to yield (Z)-(β-borylvinyl)silanes under the developed catalytic conditions.