Ir-catalysed allylic substitution: mechanistic aspects and asymmetric synthesis with phosphorus amidites as ligands
作者:Björn Bartels、Günter Helmchen
DOI:10.1039/a900864k
日期:——
Ir-catalysed allylic alkylations of enantiomerically enriched monosubstituted allylic acetates proceed with up to 79% retention of configuration using P(OPh)3 as ligand; further evidence supports the assumption of σ-allyl complexes as intermediates, and high regio- and enantioselectivity in asymmetric allylic alkylations of achiral or racemic substrates is achieved with phosphorus amidites as ligands.
Ir-catalysed allylicalkylations of enantiomerically enriched monosubstituted allylic acetates proceed with up to 87% retention of configuration using P(OPh)3 as ligand. High regio- and enantioselectivity of up to 86% ee in asymmetric allylicalkylations of achiral or racemic substrates is achieved with monodentate phosphorus amidites as ligands. Lithium N-tosylbenzylamide was identified as a suitable
使用 P(OPh)3 作为配体,Ir 催化的烯丙基烷基化对映体富集的单取代烯丙基乙酸酯的构型保留率高达 87%。以单齿磷酰胺作为配体,在非手性或外消旋底物的不对称烯丙基烷基化中实现了高达 86% ee 的高区域和对映选择性。N-tosylbenzylamide 锂被确定为适合烯丙基胺化的亲核试剂。特别重要的是使用氯化锂作为添加剂,通常会导致对映选择性增加。通过 X 射线晶体结构分析和光谱数据对两种 (π-烯丙基) IrIII 配合物进行了表征。
Carbocycles via enantioselective inter- and intramolecular iridium-catalysed allylic alkylations
Carbocycles with > 90% ee were prepared via Ir-catalysed asymmetric allylic alkylation/ring closing metathesis sequences or enantioselective Ir-catalysed intramolecular allylic alkylations.
An Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxide is described. Asymmetric allylic alkylation of terminal allylic carbonates proceeded using 5 mol % of Ir catalyst, 5 mol % of DIAPHOX 1i, 10 mol % of NaPF6, 10 mol % of LiOAc, and N,O-bis(trimethylsilyl)acetamide (BSA), affording the corresponding branched products in excellent yield and in up to 95% ee. The developed
[GRAPHICS]Rhodium-catalyzed asymmetric allylic alkylation of 1-substituted 2-propenyl acetates with dimethyl malonate proceeded with high enantioselectivity in the presence of cesium carbonate as a base and a rhodium catalyst generated from Rh(dpm)(C2H4)(2) (dpm = dipivaloylmethanato) and a chiral phosphino-oxazoline whose basic skeleton is axially chiral binaphthyl to give branch alkylation products in greater than 90% ee.