- Enantioselective Conjugate Azidation of α,β-Unsaturated Ketones under Bifunctional Organocatalysis by Direct Activation of TMSN3
-
An enantioselective organocatalytic conjugate azidation of α,β-unsaturated ketones is presented. A bifunctional organocatalyst activates TMSN3, triggering the nucleophilic addition of the azido group to enones in absence of external promoters and avoiding the direct use or the pre-formation of highly toxic and explosive hydrazoic acid. This protocol proceeds with excellent enantiocontrol under mild conditions. DFT calculations and mechanistic trials have been performed in order to demonstrate the direct activation performed by the bifunctional organocatalyst. (Figure presented.).
- Humbrías-Martín, Jorge,Pérez-Aguilar, M. Carmen,Mas-Ballesté, Rubén,Dentoni Litta, Antonella,Lattanzi, Alessandra,Della Sala, Giorgio,Fernández-Salas, Jose A.,Alemán, José
-
supporting information
p. 4790 - 4796
(2019/09/16)
-
- Copper-Catalyzed Asymmetric Conjugate Addition of Dimethylzinc to Acyl-N-methylimidazole Michael Acceptors: A Powerful Synthetic Platform
-
An efficient copper-catalyzed enantioselective conjugate addition of dimethylzinc to α,β- and α,β,γ,δ-unsaturated 2-acyl-N-methylimidazoles has been achieved using a chiral bidentate hydroxyalkyl-NHC ligand. The reactions proceeded with both excellent regio- and enantioselectivity (14 examples, 87-95 % ee) to afford the desired 1,4-adducts, which were easily transformed to the corresponding aldehydes, esters, and ketones. Subsequently, this powerful methodology was therefore successfully applied in the synthesis of natural products. Furthermore, an iterative process was also disclosed leading to highly desirable 1,3-desoxypropionate skeletons (up to 94 % d.e.). The enantioselective conjugate addition of dimethylzinc to (poly)unsaturated 2-acyl-N-methylimidazoles proceeds under Cu catalysis with excellent regio- and enantioselectivities (up to 95 % ee). The resulting 1,4-adducts can be easily transformed to the corresponding aldehydes, esters, ketones, and amines. This methodology was successfully applied in the synthesis of 1,3-desoxypropionate subunits and natural products.
- Drissi-Amraoui, Sammy,Morin, Marie S. T.,Crévisy, Christophe,Baslé, Olivier,Marciadefigueiredo, Renata,Mauduit, Marc,Campagne, Jean-Marc
-
supporting information
p. 11830 - 11834
(2015/10/05)
-
- Tungsten(0)- and rhenium(I)-catalyzed tandem cyclization of acetylenic dienol silyl ethers based on geminal carbo-functionalization of alkynes
-
Tungsten(0)- and rhenium(I)-catalyzed reactions of acetylenic dienol silyl ethers based on the concept of geminal carbo-functionalization of alkynes are reported. Treatment of 3-siloxy-1,3-diene-7-ynes with catalytic amounts of [W(CO)6] or [ReCl(CO)5] under photoirradiation conditions gives synthetically useful bicyclo[3.3.0]octane derivatives in good yields. Extremely high catalytic activity is noted for the rhenium(I) complex. The reaction has been extended to substrates containing a nitrogen atom in their tethers. In this case, two kinds of synthetically useful heterocyclic compounds-the 2-azabicyclo[3.3.0]octane derivatives 9 and the monocyclic dihydropyrroles 10, with allenyl substituents-are obtained, and selective preparation of either product can be achieved through the use of an appropriate combination of the nitrogen substituent and the type of the rhenium(I) catalyst. The 2-azabicyclo[3.3.0]octane derivatives 9 are obtained selectively by carrying out treatment of N-Ns derivatives in the presence of [ReCl(CO) 4(PPh3)], whereas the dihydropyrrole derivatives 10 are obtained by treatment of N-Mbs derivatives with [ReCl(CO)5]/ AgSbF6. Finally, we have applied this geminal carbo-functionalization to one-carbon-elongated substrates containing N-Ts moieties in their tethers. Selective 5-exo cyclization is achieved in the presence of gold(I) or rhenium(I) catalysts, whereas 6-endo cyclization is observed on use of [W(CO) 6]. Geminal carbo-functionalization of 3-siloxy-1,3-dien-7-ynes leading to bicyclo[3.3.0]octane derivatives is achieved through electrophilic activation of alkynes by tungsten(0) and rhenium(I) catalysts (see graphic). Extremely high activity is noted for rhenium(I) catalysts. Furthermore, selective preparation of two different classes of heterocyclic compounds from 5-aza-3-siloxy-1,3-dien-7-ynes is also achieved by appropriate choice of the rhenium(I) catalyst and the protecting group on the nitrogen. Copyright
- Kusama, Hiroyuki,Karibe, Yusuke,Imai, Rie,Onizawa, Yuji,Yamabe, Hokuto,Iwasawa, Nobuharu
-
supporting information; experimental part
p. 4839 - 4848
(2011/06/21)
-
- Rhodium/diene-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated Weinreb amides
-
Rhodium/chiral diene (S,S)-3b complex has been found to effectively catalyze the 1,4-addition of arylboronic acids to α,β-unsaturated Weinreb amides, furnishing useful β-chiral Weinreb amides in high enantioselectivity. The Royal Society of Chemistry 2005.
- Shintani, Ryo,Kimura, Takahiro,Hayashi, Tamio
-
p. 3213 - 3214
(2007/10/03)
-
- Rhenium(I)-catalyzed intramolecular geminal carbofunctionalization of alkynes: Tandem cyclization of ω-acetylenic dienol silyl ethers
-
(Chemical Equation Presented) Bicycle production: The low-valent rhenium complex [ReCl(CO)5] catalyzes a tandem intramolecular cyclization reaction of ω-acetylenic dienol silyl ethers. The alkyne undergoes a geminal carbofunctionalization in the presence of 0.5-3.0 mol % [ReCl(CO) 5] under photoirradiation to give bicyclic enol silyl ethers in high yields (see scheme, TIPS = triisopropylsilyl).
- Kusama, Hiroyuki,Yamabe, Hokuto,Onizawa, Yuji,Hoshino, Takahiko,Iwasawa, Nobuharu
-
p. 468 - 470
(2007/10/03)
-
- Asymmetric synthesis of cyclic β-amino acids and cyclic amines via sequential diastereoselective conjugate addition and ring closing metathesis
-
Diastereoselective conjugate addition of lithium (S)-N-allyl-N-α-methylbenzylamide to a range of α,β-unsaturated esters followed by ring closing metathesis is used to afford efficiently a range of substituted cyclic β-amino esters in high d.e. Alternatively, conjugate addition to α,β-unsaturated Weinreb amides, functional group conversion and ring closing metathesis affords cyclic amines in high d.e. The further application of this methodology to the synthesis of a range of carbocyclic β-amino esters via conjugate addition, enolate alkylation and ring closing metathesis is also described. Application of this methodology affords, after deprotection, (S)-homoproline, (S)-homopipecolic acid, (S)-coniine and (1S,2S)-trans-pentacin.
- Chippindale, Ann M.,Davies, Stephen G.,Iwamoto, Keiji,Parkin, Richard M.,Smethurst, Christian A. P.,Smith, Andrew D.,Rodriguez-Solla, Humberto
-
p. 3253 - 3265
(2007/10/03)
-
- A new synthesis of α,β-unsaturated N-methoxy-N-methylamides
-
phenyl(N-methoxy-N-methylcarbamoylmethyl)sulfoxide 1 is prepared in 2 steps starting from N-methoxy-N-methylchloroacetamide and thiophenol. Reagent 1 is useful for homologation of alkyl halides to α,β-unsaturated N-methoxy- N-methylamide compounds.
- Beney, Chantal,Boumendjel, Ahcene,Mariotte, Anne-Marie
-
p. 5779 - 5780
(2007/10/03)
-