A facile C-H activation and functionalization of aromatic imines is presented using low-valent cobalt catalysts. Using Co(PMe3)4 as catalyst we have developed an efficient simple protocol for the C-H/hydroarylation alkynes with anti selectivity. Deuterium-labeling experiments, DFT calculations coupled use a well-defined first time shed light on elusive black box catalyzed functionalization.

N-Arenesulfonyl aldimines were prepared from aliphatic and aromatic aldehydes in a two-step transformation.

The silylzincation of terminal ynamides is achieved through a radical-chain process involving (Me3Si)3SiH and R2Zn. A potentially competing polar mechanism excluded on the basis diagnostic control experiments. unique feature this addition across C≡C bond its trans selectivity. One-pot electrophilic substitution C(sp2)-Zn by Cu(I)-mediated C-C formation subsequent manipulation C(sp2)-Si provides modular access to Z-α,β-disubstituted enamides.

The regio- and stereoselective addition of germanium zinc across the C–C triple bond nitrogen-, sulfur-, oxygen-, phosphorus-substituted terminal internal alkynes is achieved by reaction with a combination R3GeH Et2Zn. Diagnostic experiments support radical-chain mechanism β-zincated vinylgermanes that show exceptional stability are characterized NMR spectroscopy X-ray crystallography. unique feature this new radical germylzincation C(sp2)–Zn formed remains available for subsequent in situ...

Herein an extremely versatile, well-defined, low-valent cobalt catalyst [Co(PMe3)4] capable of intermolecular and intramolecular imine-directed C2-alkylation alkenylation indoles is reported. The reaction proceeds in the absence reducing agents or additives, affording a range substituted dihydropyrroloindoles high yields regioselectivities. With aid deuterium labeling studies DFT (Density Functional Theory) calculations, mechanism proposed that based on Ligand-to-Ligand Hydrogen Transfer pathway.

Abstract The organometallic multicomponent Manich reaction of secondary benzylzinc compounds is described. These reagents were efficiently prepared by direct metalation (1‐bromoethyl)benzenes in tetrahydrofuran with zinc dust. Their subsequent Mannich coupling amines and aldehydes allowed the straightforward preparation a large variety α,β‐disubstituted β‐arylethylamines yields ranging from 13% to 79%. This was found require use heated mixture acetonitrile, being essential reach good...

In the presence of 60 equivalents HMPA, condensation racemic allenylzinc derived from 1-chloro-3-trimethylsilylpropyne onto enantiopure non-alpha-branched N-tert-butanesulfinimines was proven to give access corresponding cis-ethynylaziridines as major products. The good cis selectivity observed presumably resulted a high kinetic resolution with being partially configurationally labile respect time scale defined by rate reaction. Both single crystal X-ray analysis and semiempirical...

Abstract A domino process involving Michael addition and carbocyclization has been developed starting from β‐ N ‐allylamino enoates various organometallic reagents (organozinc halides, diorganozinc reagents, copper/zinc mixed species). In all cases the mechanism of this reaction evidenced to involve a radical‐polar crossover mechanism.

An efficient methodology for the synthesis of sphingoid-type bases is reported. It involves stereoselective addition a racemic 3-alkoxy allenylzinc to enantiopure N-tert-butylsulfinyl imines and cross-metathesis reaction as key steps. has been successfully applied syntheses sphinganine naturally occurring bioactive related compounds, among which hydrolysis product clavaminol H two spisulosines. All these compounds have prepared in six steps from high overall yields (>56%).

Zinc reagents (Me2PhSi)2Zn and [(Me3Si)3Si]2Zn undergo highly regio- stereoselective addition across the carbon–carbon triple bond of nitrogen-, sulfur-, oxygen-, phosphorus-substituted terminal alkynes in absence copper or any other catalyst. Both yield exclusively β-isomers, stereoselectivity is determined by silyl group: Me2PhSi for cis (Me3Si)3Si trans. These stereodivergent silylzincation protocols offer an efficient access to heteroatom-substituted vinylsilanes with either double...

An efficient E-selective semihydrogenation of internal alkynes was developed under low dihydrogen pressure and reaction temperature from commercially available reagents: Cl2Pd(PPh3)2, Zn0, ZnI2. Kinetic studies control experiments underline the significant role ZnI2 in this process H2 atmosphere, establishing that transformation involves syn-hydrogenation followed by isomerization. This simple easy-to-handle system provides a route to E-alkenes mild conditions.

Enantiopure trans-ethynyl N-tert-butanesulfinylaziridines (RS)-6 were prepared in good to excellent yields by the condensation of racemic allenylzinc species 1 derived from 3-chloro-1-trimethylsilylpropyne onto corresponding enantiopure N-tert-butanesulfinimines (RS)-5. The absolute stereochemistry was shown be (RS,2R,3R) and results a chelate-type transition state which zinc atom is coordinated both nitogen oxygen atoms imine. Further removal N-tert-butanesulfinyl auxiliary alkyl...

The short and efficient asymmetric synthesis of (−)-1-hydroxyquinolizidinone was achieved in seven steps 25.2% overall yield from readily available 5-chloropentanal. It is a key intermediate the formal syntheses (−)-homopumilotoxin 223G (−)-epiquinamide.

Go triple! A new domino 1,4-addition/alkyne carbozincation has been developed with dialkylzinc reagents (see scheme). This radical-polar crossover sequence involves a novel stereoselective radical zinc atom transfer that leads to vinyl species can be reacted electrophiles, thus offering multicomponent approach polysubstituted alkylidene tetrahydrofurans. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2111/2008/z801451_s.pdf or from...

A domino 1,4-addition/alkyne carbozincation sequence based on a radical zinc-atom transfer process is disclosed. Two efficient multicomponent approaches to 3-alkylidenetetrahydrofurans from β-(propargyloxy)enoates bearing pendant alkynes (including ynamides) have been established: one involving the direct addition of dialkylzincs, and second dimethylzinc-mediated alkyl iodides. Both sequences utilize stereoselective formation intermediate alkylidenezincs well suited for in situ...

Abstract The stereoselective synthesis of syn ‐β‐amino propargylic ethers by the addition racemic lithio 3‐(methoxymethoxy)allenylcuprates, and more particularly (cyano) (mesityl)cuprates, to enantiopure chiral N‐tert ‐butylsulfinylimines is reported. scope limitations reaction studied. usefulness methodology for compounds having a ‐1,2‐amino alcohol unit shown through development asymmetric syntheses (+)‐β‐conhydrine an advanced intermediate (−)‐balanol.

The asymmetric synthesis of (−)-swainsonine and (−)-8-epi-swainsonine is reported through the addition either allenylzinc or allenyl lithio cyanocuprate reagents derived from [3-(methoxymethoxy)prop-1-ynyl]trimethylsilane to enantiopure α,β-dialkoxy N-tert-butanesulfinylimines d-erythronolactone.

Syntheses of alkynyl- oxiranes and aziridines are rewieved. These compounds can serve as substrates in ring opening reactions with carbon nucleophiles to give allenyl- or homopropargylalcohols amines. Keywords: oxirane, aziridine, reaction, homopropargylalcohots, homopropargylamines

Substituted vinylidene zinc carbenoids undergo a Fritsch−Buttenberg−Wiechell rearrangement. The migratory aptitude of the two groups R/R1 was studied by 13C labeling experiments and depends on degree substitution in R R1 presence an oxygen atom allylic position.

The short and efficient synthesis of (−)-α-conhydrine was accomplished with 41% overall yield in seven steps high diastereo- enantioselectivity. anti-stereochemistry the two stereogenic centers has been confirmed by single-crystal X-ray analysis an intermediate.