The methylenation of beta-lactones 5 with dimethyltitanocene provides a versatile, reliable, and highly chemoselective entry to 2-methyleneoxetanes 7. The conversion proceeds selectively in the presence of alkenes, unprotected alcohols, and a variety of other carbonyl moieties, A study of conditions for the optimization of this reaction is delineated. In addition, the first X-ray structure of a 2-methyleneoxetane, which shows its similarity to related p-lactones, is reported. Reactivity studies of 2-methyleneoxetanes are presented in which it is demonstrated that these compounds are attacked at C-4 with a nucleophile; then, subsequently, the resultant enolate reacted with an electrophile. An interesting dichotomy of reactivity was observed when methyleneoxetane 7c was treated with electrophiles. Reaction of 7c with acetic acid gave acetoxyoxetane 19. When 7c was exposed to bromine, dibromoketone 20 resulted.
Diversity-Oriented Approach to Macrocyclic Cyclophane Derivatives via Ring-Closing Metathesis
作者:Sambasivarao Kotha、Mukesh Shirbhate
DOI:10.1055/s-0032-1317020
日期:——
A short synthetic approach to the macrocyclic framework of longithorone C is described via ring-closingmetathesis using the Grubbs 2nd generation catalyst.
使用 Grubbs 第二代催化剂,通过闭环复分解反应描述了长环酮 C 大环骨架的简短合成方法。
Selenium-mediated cyclization reactions of alkenyl-substituted β-ketoesters
作者:William P. Jackson、Steven V. Ley、Alan J. Whittle
DOI:10.1039/c39800001173
日期:——
Phenylselenating agents, in which the counter ion is non-nucleophilic, react with certain alkenyl-substitutedβ-ketoesters to afford cyclized products, some of which can be further rearranged using SnCl4.
Supramolecular polymerization of a ureidopyrimidinone-based [2]catenane prepared <i>via</i>
ring-closing metathesis
作者:Abraham J. P. Teunissen、José Augusto Berrocal、Christiaan H. W. A. Corbet、E. W. Meijer
DOI:10.1002/pola.28694
日期:2017.9.15
The synthesis and supramolecular polymerization of a ureidopyrimidinone-based Sauvage-type [2]catenane is reported. The monomer synthesis explores many routes using the elegant metathesis catalysts of Bob Grubbs, yielding a catenane with one ureidopyrimidinone in each cycle. The supramolecular polymer obtained features both mechanical bonds and quadruple hydrogen bonding connections.
Cyclisation reactions of alkenyl β-ketoesters involving a novel phenylseleno group migration
作者:William P. Jackson、Steven V. Ley、Judith A. Morton
DOI:10.1016/s0040-4039(01)90531-3
日期:1981.1
A number of alkenyl-substituted α-phenylseleno β-ketoesters can be cyclised in the presence of acidic catalysts in which a novel migration of phenylseleno moiety occurs.
Kotha, Sambasivarao; Shirbhate, Mukesh E., Indian Journal of Chemistry - Section B Organic and Medicinal Chemistry, 2015, vol. 54B, # 12, p. 1483 - 1494