A general catalytic oxo-hetero-Diels−Alder reaction for pro-chiral aldehyde and ketone N-oxy-pyridines is presented. The catalytic and asymmetric oxo-hetero-Diels−Alder reaction of electron-rich dienes with N-oxy-pyridine-2-carbaldehyde and ketone derivatives, catalyzed by chiralcopper(II)−bisoxazoline complexes, gives optically active six-membered oxygen heterocycles in moderate to good yields and
Asymmetric Synthesis of Adjacent Tri‐ and Tetrasubstituted Carbon Stereocenters: Organocatalytic Aldol Reaction of an Hydantoin Surrogate with Azaarene 2‐Carbaldehydes
作者:June Izquierdo、Noémie Demurget、Aitor Landa、Tore Brinck、Jose M. Mercero、Peter Dinér、Mikel Oiarbide、Claudio Palomo
DOI:10.1002/chem.201902817
日期:2019.9.20
A bifunctional amine/squaramide catalyst promoted direct aldol addition of an hydantoin surrogate to pyridine 2-carbaldehyde N-oxides to afford adducts bearing two vicinal tertiary/quaternary carbons in high diastereo- and enantioselectivity (d.r. up to >20:1; ee up to 98 %) is reported. Acid hydrolysis of adducts followed by reduction of the N-oxide group yields enantiopure carbinol-tethered quaternary
Azine-N-oxides as effective controlling groups for Rh-catalysed intermolecular alkyne hydroacylation
作者:Daniel F. Moseley、Jagadeesh Kalepu、Michael C. Willis
DOI:10.1039/d1sc03915f
日期:——
aldehydes that contain a free N-lone pair. We demonstrate conversion of the hydroacylation products to the corresponding azine, through a one-pot hydroacylation/deoxygenation sequence. A one-pot hydroacylation/cyclisation, using N-Boc propargylamine, additionally leads to the synthesis of a bidentate pyrrolyl ligand.
杂环衍生的醛是金属催化加氢酰化化学中具有挑战性的底物。我们表明,通过使用吖嗪N-氧化物取代的醛,可以获得良好的反应性,并且它们是炔烃分子间加氢酰化的高效底物。使用Rh( I )-催化剂,我们实现了温和且可扩展的醛C-H活化,允许与未活化的末端炔烃偶联,具有良好的收率和高区域选择性(高达>20:1l:b)。两种底物都可以耐受多种官能团。该反应也适用于含有游离 N-孤电子对的二嗪醛。我们展示了通过一锅加氢酰化/脱氧序列将加氢酰化产物转化为相应的吖嗪。使用 N-Boc 炔丙胺的一锅加氢酰化/环化另外导致二齿吡咯基配体的合成。
Bis(oxazoline) Lewis Acid Catalyzed Aldol Reactions of PyridineN-Oxide Aldehydes—Synthesis of Optically Active 2-(1-Hydroxyalkyl)pyridine Derivatives: Development, Scope, and Total Synthesis of an Indolizine Alkaloid
A new, short, and simplified procedure for the synthesis of optically active pyridine derivatives from pro-chiral pyridine-N-oxides is presented. The catalytic and asymmetric Mukaiyama aldol reaction between ketene silyl acetals and 1-oxypyridine-2-carbaldehyde derivatives catalyzed by chiral copper(II)-bis(oxazoline) complexes gave optically active 2-(hydroxyalkyl)- and 2-(anti-1,2-dihydroxyalkyl)pyridine