A highly active diradical cobalt(<scp>iii</scp>) catalyst for the cycloisomerization of alkynoic acids
作者:Nicolas Leconte、Amaury du Moulinet d'Hardemare、Christian Philouze、Fabrice Thomas
DOI:10.1039/c8cc04459g
日期:——
The first cobalt-catalysed cycloisomerisation of alkynoicacids is reported, thanks to the design of a well-defined diradical cobalt(III) catalyst, in the absence of any additives. The high efficiency, regioselectivity and chemoselectivity are comparable to those of noble metal-based systems. The unique reactivity might be attributed to second coordination sphere effects.
Cyclization of alkynoic acids with gold catalysts: a surprising dichotomy between AuI and AuIII
作者:Hassina Harkat、Albert Yénimégué Dembelé、Jean-Marc Weibel、Aurélien Blanc、Patrick Pale
DOI:10.1016/j.tet.2008.10.112
日期:2009.2
ω-Acetylenic acids, substituted or not at their acetylenic end, could be efficiently cyclized to γ- or δ-alkylidene lactones in the presence of AuCl and K2CO3. In contrast AuCl3 led to lactone dimers, probably through cyclization and reductive dimerization. These AuI and AuIII catalyzed cyclizations were totally regioselective and most often highly stereoselective.
在AuCl和K 2 CO 3的存在下,可以在其乙炔基末端取代或不取代的ω-乙炔酸有效地环化为γ-或δ-亚烷基内酯。相反,AuCl 3可能通过环化和还原性二聚而导致内酯二聚体。这些Au I和Au III催化的环化反应完全是区域选择性的,并且通常是高度立体选择性的。
Stereospecific synthesis of -2-alkenylcyclopropane carboxylic acids; A total synthesis of (±)--chrysanthemic acid
作者:Andrew G. Cameron、David W. Knight
DOI:10.1016/s0040-4039(00)98675-1
日期:1985.1
A stereospecific route to cis-2,2-dimethyl-3-alkenyl-cyclopropanecarboxylic Acids is illustrated by a total synthesis of (±)-cis-Chrysanthemic Acid (11). The key step consists of an alicyclic Claisenrearrangement of O-silyl enolates derived from appropriately substituted (Z)-4-hexen-6-olides [e.g.(9)].
Facile synthesis of 3,4-dihydro-4,4-dimethyl-2H-pyran-2-one via palladium catalyzed terminal oxidation of 3,3-dimethyl-4-pentenoates
作者:Mariko Tanaka、Hisao Urata、Takamasa Fuchikami
DOI:10.1016/s0040-4039(00)84744-9
日期:——
Selective terminal oxidation of 3,3-dimethyl-4-pentenoates does occur under chloride-free Wacker conditions [Pd(OAc)2/O2] in AcOH to give 5-acetoxy-3,3-dimethyl-4-pentenoates (7) and their analogues (2, 8) in good yields. Successive cyclization of 7 and 8 at vapor phase pyrolysis on SiO2 affords 3,4-dihydro-4,4-dimethyl-2H-pyran-2-one (1).
在无氯的Wacker条件下[Pd(OAc)2 / O 2 ]在AcOH中确实发生3,3-二甲基-4-戊烯酸酯的选择性末端氧化,得到5-乙酰氧基-3,3-二甲基-4-戊烯酸酯(7 )及其类似物(2,8),收率很高。在SiO 2上进行气相热解时,将7和8连续环化,得到3,4-二氢-4,4-二甲基-2H-吡喃-2-酮(1)。
Sulfidkontraktion<i>via</i>alkylative Kupplung: Eine methode zur darstellung von β-dicarbonylderivaten. Über synthetische methoden, 1. Mitteilung
作者:M. Roth、P. Dubs、E. Götschi、A. Eschenmoser
DOI:10.1002/hlca.19710540229
日期:——
The experiments described in reaction schemes 1–12 indicate that sulfide contraction via alkylative coupling (see scheme p. 729) is a potentially general method for the synthesis of secondary vinylogous amides and enolizable β-dicarbonyl compounds.