28315-20-0Relevant academic research and scientific papers
Regio- And diastereoselective Pd-catalyzed aminochlorocyclization of allylic carbamates: scope, derivatization, and mechanism
Ariga, Elaine Miho,Carita Correra, Thiago,Matsushima, Jullyane Emi,McIndoe, J. Scott,Moreira Ribeiro, Francisco Wanderson,Omari, Isaac,Papa Spadafora, Bruna,Rodrigues, Alessandro,Soares, Priscila Machado Arruda,Vinhato, Elisangela,de Oliveira-Silva, Diogo
supporting information, p. 5595 - 5606 (2021/07/02)
The regio- and diastereoselective synthesis of oxazolidinonesviaa Pd-catalyzed vicinal C-N/C-Cl bond-forming reaction from internal alkenes of allylic carbamates is reported. The oxazolidinones are obtained in yields of 44 to 95% with high to excellent diastereoselectivities (from 6?:?1 to >20?:?1 dr) from readily available precursors. This process is scalable, and the products are suitable for the synthesis of useful amino alcohols. A detailed theoretical and experimental mechanistic study was carried out to describe that the reaction proceeds through ananti-aminopalladation of the alkene followed by an oxidative C-Pd(ii) cleavage with retention of the carbon stereochemistry to yield the major diastereomer. The role of Cu(ii) in a C-Cl bond-forming mechanism step has also been proposed.
Lithium choreography: Intramolecular arylations of carbamate-stabilised carbanions and their mechanisms probed by in situ IR spectroscopy and DFT calculations
Fournier, Anne M.,Nichols, Christopher J.,Vincent, Mark A.,Hillier, Ian H.,Clayden, Jonathan
supporting information, p. 16478 - 16490 (2013/02/23)
Deprotonation of O-allyl, O-propargyl or O-benzyl carbamates in the presence of a lithium counterion leads to carbamate-stabilised organolithium compounds that may be quenched with electrophiles. We now report that when the allylic, propargylic or benzylic carbamate bears an N-aryl substituent, an aryl migration takes place, leading to stereochemical inversion and C-arylation of the carbamate α to oxygen. The aryl migration is an intramolecular S NAr reaction, despite the lack of anion-stabilising aryl substituents. Our in situ IR studies reveal a number of intermediates along the rearrangement pathway, including a "pre-lithiation complex," the deprotonated carbamate, the rearranged anion, and the final arylated carbamate. No evidence was obtained for a dearomatised intermediate during the aryl migration. DFT calculations predict that during the reaction the solvated Li cation moves from the carbanion centre, thus freeing its lone pair for nucleophilic attack on the remote phenyl ring. This charge separation leads to several alternative conformations. The one having Li+ bound to the carbamate oxygen gives rise to the lowest-energy transition structure, and also leads to inversion of the configuration. In agreement with the IR studies, the DFT calculations fail to locate a dearomatised intermediate. Dancing to lithium's tune: In situ IR spectroscopy and DFT calculations allow the detailed pathways of aryl migrations taking place in lithiated carbamates to be characterised (see scheme).
Practical synthesis of allylic silanes from allylic esters and carbamates by stereoselective copper-catalyzed allylic substitution reactions
Oestreich, Martin,Auer, Gertrud
, p. 637 - 640 (2007/10/03)
The first copper-catalyzed allylic substitution reactions of allylic acetates and carbamates employing a bis(triorganosilyl)zinc reagent are reported. This novel procedure avoids the use of stoichiometric amounts of copper salts which are usually mandatory with this chemistry. Application of this methodology to standard model substrates substantiates a high diastereoselectivity for the double bond geometry (E:Z) as well as the relative configuration (syn:anti).
