Photochemical Rearrangement of <i>N</i>-Mesyloxylactams: Stereospecific Formation of <i>N</i>-Heterocycles
作者:Alexandre Drouin、Dana K. Winter、Simon Pichette、Samuel Aubert-Nicol、Jean Lessard、Claude Spino
DOI:10.1021/jo101805q
日期:2011.1.7
N-Mesyloxylactams undergo an efficient ring-contraction to N-heterocycles of various ring sizes. Yields increase with the degree of substitution α to the carbonyl. The stereochemical information of a chiral migrating carbon is conserved making this reaction a synthetically useful complement to the well-known Hofmann, Curtius, Lossen, and Schmidt rearrangements.
N‐alkoxy group played important roles in this reaction. First, it removed the requirement for an extra preactivation step prior to nucleophilic addition to activate inert amide carbonyl groups. Second, the N‐alkoxy group formed a five‐membered chelated complex after the firstnucleophilic addition, resulting in suppression of an extra addition of the firstnucleophile. While diisobutylaluminum hydride (DIBAL‐H)
A new approach to cyclic hydroxamic acids: intramolecular cyclization of N-benzyloxy carbamates with carbon nucleophiles
作者:Yuan Liu、Hollie K. Jacobs、Aravamudan S. Gopalan
DOI:10.1016/j.tet.2011.01.073
日期:2011.3
moderate yields. The sulfoneintermediates 3 from this study can be alkylated while the corresponding phosphonates have been shown to undergo HWE reaction. The α,β-unsaturated synthon, 8, prepared by thermal elimination of sulfoxide 3m, undergoes Michael addition with secondary amines. The usefulness of this approach to prepare polydentate chelators has been demonstrated by the synthesis of bis cyclic hydroxamic
Approach to Fully Substituted Cyclic Nitrones from
<i>N</i>
‐Hydroxylactam Derivatives: Development and Application to the Total Synthesis of Cylindricine C
An approach to cyclic nitrones from N‐hydroxylactam derivatives is documented. The nucleophilic addition of an organolithium reagent to an N‐OSEM [SEM=2‐(trimethylsilyl)ethoxymethyl] lactam forms a five‐membered chelated intermediate, which undergoes both elimination and deprotection to give a fully substituted nitrone in a one‐pot process. When combined with the N‐oxidation of easily available chiral
从N-羟基内酰胺衍生物制备环状硝酮的方法已有文献记载。有机锂试剂向N- OSEM [SEM = 2-(三甲基甲硅烷基)乙氧基甲基]内酰胺的亲核加成反应形成五元螯合的中间体,该中间体经过消除和脱保护作用,可以一锅法得到完全取代的硝酮。当与容易获得的手性内酰胺的N氧化结合使用时,该方法对于快速合成对映纯形式的手性硝酮特别有用,可实现简明的cylindricine C的全合成。
Synthesis of isolable β-chloroenamines from <i>N</i>-alkoxylactams with organometallic reagents
An efficient approach to access isolable β-chloroenamines via nucleophilic addition/dehydration of α-chloro N-alkoxylactam with organolithium and Grignardreagents is reported. This approach is amenable to the synthesis of β-chloroenamines by incorporating various C(sp) and C(sp2) units, such as alkyne, aryl, and heteroaryl moieties. The sequential reaction has a broad substrate scope and can be carried