Generation of 2-(trimethylsiloxy)allyl cations and their reactions with 1,3-dienes. Change in mechanism of 3 + 4 .fwdarw. 7 cycloaddition with solvent
作者:Nobujiro Shimizu、Masayuki Tanaka、Yuho Tsuno
DOI:10.1021/ja00369a031
日期:1982.3
werden mit AgClO4 entsprechende Silyloxy-allyl- Kationen, z.B. (XIII) [aus (Ia)], erzeugt, die in Nitromethan z.B. mit Furan (II) unter Bildung der Addukte (III)+(IV) bzw. (VI) [neben (VIb)-(VIe) auch die Isomeren (VII) bzw. (VIII)] bzw. (X) [neben (Xb), (Xc) auch die Isomeren (XI) bzw. (XII)] reagieren (Diskussion des Reaktionsmechanismus).
Aus den Trimethylsilyloxy-allylchloride (I), (V), (IX) werden mit AgClO4 entsprechende Silyloxy-allyl-Kationen, zB (XIII) [aus (Ia)], erzeugt, die in Nitromethan zB mit Furan (II) under Bildung der Addukte (III)+(IV) bzw。(VI) [neben (VIb)-(VIe) auch die Isomeren (VII) bzw. (八)】bzw。(X) [neben (Xb), (Xc) auch die Isomeren (XI) bzw. (XII)]反应器(Diskussion des Reaktionsmechanismus)。
Solvent-free preparation of α,α-dichloroketones with sulfuryl chloride
作者:Dewei Tu、Juan Luo、Wengao Jiang、Qiang Tang
DOI:10.1016/j.tetlet.2021.153335
日期:2021.9
An efficient and facile method is reported for the synthesis of a series of α,α-dichloroketones. The direct dichlorination of methyl ketones and 1,3-dicarbonyls using an excess amount of sulfuryl chloride affords the corresponding -dichloro compounds in moderate to excellent yields. Moreover, the protocol features high yields, broad substrate scope, and simple reaction conditions without using any
A new synthetic method of conjugated enones by the use of carbanion-induced Favorskii-typerearrangement is described. The reaction of α,α′-dihalo ketones R1R2(X)CC(O)CH2X with sodiomalonates Na+ −CR3(CO2R4)2 in THF at 0°C—room temperature gave conjugated enones R1R2C=CHC(O)CR3(CO2R4)2 in 42–66% yields. The reaction can be also adaptable to the enolates of ethyl cyanoacetate or malononitrile to give
1,1-Dichloro- and 1,3-dichloro-2-alkanones react with 2-methylfuran in the presence of lithium perchlorate/triethylamine to form 2-chloro-1-methyl-8-oxabicyclo [3.2.1]oct-6-ene-3-ones predominantly.
Favorskii-Type Rearrangement of α,α′-Dihalo Ketones Induced by Enolates of (Diethoxyphosphinyl)acetic Esters and Its Application to the Synthesis of α,α′-Divinyl Ketones
A Favorskii-type rearrangement of 1,3-dihalo-3-methyl-2-butanone with enolate of ethyl (diethoxyphosphinyl)acetate or t-butyl (diethoxyphosphinyl)acetate gave ethyl 2-(diethoxyphosphinyl)-5-methyl-3-oxo-4-hexenoate (3a) or its t-butyl ester (3b). Compound 3b was applied to the preparation of (E)-5-methyl-1-(p-tolyl)-1,4-hexadien-3-one and diethyl (4-methyl-2-oxo-3-pentenyl)phosphonate, which are the important intermediates for natural product syntheses.