Achiral Counterion Control of Enantioselectivity in a Brønsted Acid-Catalyzed Iodolactonization
作者:Mark C. Dobish、Jeffrey N. Johnston
DOI:10.1021/ja301858r
日期:2012.4.11
Highly enantioselective halolactonizations have been developed that employ a chiral proton catalyst-N-iodosuccinimide (NIS) reagent system in which the Brønsted acid is used at catalyst loadings as low as 1 mol %. An approach that modulates the achiral counterion (equimolar to the neutral chiral ligand-proton complex present at low catalyst loadings) to optimize the enantioselection is documented for
Catalytic Asymmetric Iodocyclization of<i>N-</i>Tosyl Alkenamides using Aminoiminophenoxy Copper Carboxylate: A Concise Synthesis of Chiral 8-Oxa-6-Azabicyclo[3.2.1]octanes
A newly developed aminoiminophenoxycoppercarboxylate (L7‐Cu‐OAc)‐catalyzed asymmetriciodocyclization of N‐Tosyl alkenamides gave O‐cyclized products in good yields with high enantioselectivity. From the O‐cyclized products, a skeletal transformation was succeeded in the synthesis of biologically important chiral 8‐oxa‐6‐azabicyclo[3.2.1]octanes. DFT calculations suggested that the acetoxy anion
A 3,3'-bis(aminoimino)BINOL ligand was newly designed and synthesized for the formation of a trinuclear Zn complex upon reaction with Zn(OAc)2. Using the harmony of the tri-zinc atoms, 1 mol% Zn3(OAc)4-3,3'-bis(aminoimino)binaphthoxide catalyzed asymmetriciodolactonization in up to 99.9% ee.
The Role of Ni-Carboxylate During Catalytic Asymmetric Iodolactonization Using PyBidine-Ni(OAc)2
作者:Takayoshi Arai、Satoshi Kajikawa、Eri Matsumura
DOI:10.1055/s-0033-1339676
日期:——
The combination of a PyBidine-Ni(OAc)(2) complex with a catalytic amount of iodine efficiently catalyzed asymmetric iodolactonization to generate chiral iodolactones with up to 89% enantiomeric excess. The formation of an intermediate Ni-carboxylate species from the alkenyl carboxylic acid is a key role in promoting the iodolactonization.