Diastereoselective Synthesis of β-Lactam-Oxindole Hybrids Through a Three-Component Reaction of Azetidine-2,3-diones, α-Diazo-oxindoles, and Alcohols Catalyzed by [Rh2(OAc)4]
β-Lactam–oxindolehybrids have been synthesized in good yields in a one-pot procedure through efficient and stereoselective capture of an oxonium ylide with azetidine-2,3-diones. The reaction allows high to moderate control of stereoselectivity, depending on the 3-diazo-oxindole precursor and the hydroxylic compound used. Two new quaternary stereogenic centers were formed; the stereochemistry at the
通过用氮杂环丁烷-2,3-二酮有效和立体选择性地捕获氧鎓叶立德,已经在一锅法中以良好的产率合成了β-内酰胺-羟吲哚杂化物。根据所使用的 3-重氮-羟吲哚前体和羟基化合物,该反应允许对立体选择性进行高到中等控制。形成了两个新的四元立体中心;C-3 季中心的立体化学由 C-4 上的大取代基控制,而相邻的第二季立体中心的立体选择性由 α-重氮-羟吲哚控制。两个四元中心的立体化学已通过单晶 X 射线衍射明确指定。
Divergent Reactivity of 2-Azetidinone-Tethered Allenols with Electrophilic Reagents: Controlled Ring Expansion<i>versus</i>Spirocyclization
A dual reactivity of 2‐azetidinone‐tethered allenols may occur by judicious choice of the electrophilicreagents, namely halogenating versus selenating reagents. Using common substrates, structurally different compounds, namely tetramic acids (from N‐bromosuccinimide) or spirocyclic seleno‐β‐lactams (from N‐phenylselenophthalimide), can be readily synthesized by these divergent protocols.
Rhodium-Catalyzed Synthesis of 3-Hydroxy-β-lactams via Oxonium Ylide Generation: Three-Component Reaction between Azetidine-2,3-diones, Ethyl Diazoacetate, and Alcohols
actams, with two new adjacent stereogenic centers, have been prepared in a single step by a rhodium-catalyzed, three-component reactionbetween azetidine-2,3-diones, ethyl diazoacetate, and alcohols. Good to moderate stereoselectivity was obtained depending on the alcohol used. The stereochemistry of the new centers has been undoubtedly assigned by single crystal X-ray diffraction.
Metal-Catalyzed Cycloisomerization and Tandem Oxycyclization/Hydroxylation of Alkynols: Synthesis of Nonfused, Spiranic and Fused Oxabicyclic β-Lactams
作者:Benito Alcaide、Pedro Almendros、Teresa Martínez del Campo、Rocío Carrascosa
DOI:10.1002/ejoc.201000710
日期:2010.9
2-Azetidinone-tethered alkynols, readily prepared from the corresponding aldehydes or ketones, were used as starting materials for the oxycyclization reaction catalyzed by precious metals. AgOAc exclusively affords dihydrofurans, methylenetetrahydrofurans, or methylenetetrahydro-2H-pyrans through specific 5-endo, 5-exo, or 6-exo pathways, respectively. Interestingly, in the presence of a catalytic amount of Pt"
2-氮杂环丁酮链炔醇,很容易从相应的醛或酮制备,被用作贵金属催化氧环化反应的原料。AgOAc 分别通过特定的 5-endo、5-exo 或 6-exo 途径专门提供二氢呋喃、亚甲基四氢呋喃或亚甲基四氢-2H-吡喃。有趣的是,在催化量的 Pt" 或 Au III 盐的存在下,环化反应优先通过炔醇的串联氧环化/羟基化发生,以中等至高产率提供各种非稠合、螺旋和稠合氧杂双环 β-内酰胺。此外,已经观察到可以完成串联金催化的甲氧基甲基炔基醚的环醚化/羟基化。
A convenient synthesis of azetidine-2,3-diones (α-Keto-β-Lactams)