Rh-Catalyzed Conjugate Addition of Aryl and Alkenyl Boronic Acids to α-Methylene-β-lactones: Stereoselective Synthesis of <i>trans</i>-3,4-Disubstituted β-Lactones
作者:Christian A. Malapit、Irungu K. Luvaga、Donald R. Caldwell、Nicholas K. Schipper、Amy R. Howell
DOI:10.1021/acs.orglett.7b01994
日期:2017.9.1
A one-step preparation of 3,4-disubstituted β-lactones through Rh-catalyzed conjugate addition of aryl or alkenylboronicacids to α-methylene-β-lactones is described. The operationally simple, stereoselective transformation provides a broad range of β-lactones from individual α-methylene-β-lactone templates. This methodology allowed for a direct, final-step C-3 diversification of nocardiolactone,
Unusual, Strained Heterocycles: 3-Alkylidene-2-methyleneoxetanes from Morita−Baylis−Hillman-type Adducts
作者:Isamir Martínez、Alexander E. Andrews、Joseph D. Emch、Albert J. Ndakala、Jun Wang、Amy R. Howell
DOI:10.1021/ol020202v
日期:2003.2.1
[GRAPHICS]3-Alkylidene-2-methyleneoxetanes have been prepared by treating alpha-alkylidene-beta-lactones, derived from Morita-Baylis-Hillman-type adducts, with dimethyltitanocene. Preliminary studies of the reactivity of these little known, strained heterocycles are also described.
Cross Metathesis with Strained Exocyclic Enones: Synthesis of 3-Alkylideneoxetan-2-ones from 3-Methyleneoxetan-2-ones
作者:Ravinder Raju、Amy R. Howell
DOI:10.1021/ol060624v
日期:2006.5.1
3-Alkylideneoxetan-2-ones have been prepared in good to excellent yields with high Z-selectivity by olefin cross metathesis with 3-methyleneoxetan-2-ones in the presence of second generation metathesis catalysts 1 or 2.
Pd-Catalyzed Acyl C–O Bond Activation for Selective Ring-Opening of α-Methylene-β-lactones with Amines
作者:Christian A. Malapit、Donald R. Caldwell、Nicole Sassu、Samuel Milbin、Amy R. Howell
DOI:10.1021/acs.orglett.7b00494
日期:2017.4.21
A Pd-catalyzed ring-opening of beta-lactones with various types of amines (primary, secondary, and aryl) to provide beta-hydroxy amides with excellent selectivity toward acyl C-O bond cleavage is reported. The utility of this protocol is demonstrated in an asymmetric kinetic resolution providing enantioenriched a-methylene-beta-lactones.
Strain‐Driven Dyotropic Rearrangement: A Unified Ring‐Expansion Approach to α‐Methylene‐γ‐butyrolactones
dyotropic rearrangement of α‐methylene‐β‐lactones has been realized, which enables the efficient access of a wide range of α‐methylene‐γ‐butyrolactones displaying remarkable structural diversity. Several appealing features of the reaction, including excellent efficiency, high stereospecificity, predictable chemoselectivity and broad substrate scope, render it a powerful tool for the synthesis of MBL‐containing