Propargyl vinyl ether

The Claisen rearrangement of propargyl vinyl ethers directly delivers the allene no equilibrium is observed. This reaction was also successful with complex substrates in order to show this, of numerous examples [375, 513-536], the compounds 159 [537] and 161 [538] are depicted (Scheme 1.71). 

Thermal propargyl rearrangement-Claisen rearrangement of propargyl vinyl ethers and Cope-type rearrangements of propargyl malonates [93]. 

The use of propargyl vinyl ethers prompted Toste et al. to develop a stereoselective preparation of 2-hydroxy-3,6-dihydropyrans, suitable for the synthesis of spirocyclic compounds. The reaction was catalyzed by a small amount (1 mol%) of [0(AuPPh3)3]... 

A range of highly substituted 277-pyrans has been synthesised from propargyl vinyl ethers (Scheme 1). Catalysis by Ag(I) results in rearrangement of the propargyl moiety to an allenic system. Isomerisation in DBU leads to a dienone which spontaneously electrocyclises to the stable pyran. In some instances ftirans arising from a 5-exo cyclisation are also formed and in... 

Dihydro-2-hydroxypyrans are formed from propargyl vinyl ethers in a Au(I)-catalysed Claisen rearrangement - heterocyclisation sequence in wet dioxane. Stereochemical features in the substrate are retained in the product. Incorporation of an alkanol function adjacent to the O atom results in the formation of spiroketals (Scheme 3) <06JA8132>. [3-Hydroxyallenes... 

Au-Catalyzed reaction of propargyl vinyl ethers furnished tri- and tetrasubstituted furans in high yields. The reaction proceeded through cyclization of 2-allenyl-13-dicarbonyl intermediates produced from propargyl-Claisen rearrangement <05OL3925>. 

So liefert l,l-Bis-[propargyloxy]-ethan beim Oberleiten der Dampfe iiber Dimolybdantrioxid bei 300° (2 Sek.) 52% 3,4-Pentadienal neben 27% Propargyl-vinyl-ether und 87% Propargylalkohol176. 

For the design of organometallic catalytic reactions, one can apply stereoelectronic effects that are specific to the metal centers, such as the trans-effect. An interesting manifestation of this effect in the Rh-catalyzed Claisen rearrangement of propargyl vinyl ethers (Figure 11.13) was found in the computational analysis of this process. ... 

Figure 11.14 Energy profile of the Rh-catalyzed Claisen rearrangement of propargyl vinyl ethers initiated by coordination at the alkyne. Red and gray depict the cis and the trans orientations, respectively, of CO relative to substrate at the Rh center. Energies were calculated relative to the most stable Rh(l)-vinyl ether complex at the M05-2X/LANL2DZ level.

Vidhani, D. V., Krafft, M. E., Alabugin, I. V. (2014). Rh(I)-Catalyzed Transformation of Propargyl Vinyl Ethers into , Z)-Dienals Stereoelectronic Role of trans Effect in a Metal-Mediated PericycUc Process and a Shift from Homogeneous to Heterogeneous Catalysis During a One-Pot Reaction. Journal of Organic Chemistry, 79, 352-364. 

Propargyl Vinyl Ethers as Powerful Starting Points for Heterocycle Synthesis... 

Scheme 1 The principle of furan synthesis from propargyl vinyl ethers.

Our studies on the use of this rearrangement process for the synthesis of heterocycles began in 2005 (05OL3925,060BC2076), when we developed an operationally simple and reliable procedure to synthesize tri- and tetrasubstituted ffirans 8 in good yields under neutral and mild conditions (Scheme 3).The procedure used propargyl vinyl ethers 6 as starting materials... 

It is of note that both the Z-configured and the E-configured propargyl vinyl ethers 6 react to give the same heterocyclic products 8. As the diaste-reoselectivity in the course of the preparation of the propargyl vinyl ether starting materials 6 is not always easy to control, this result allows for the... 

In 2011,Jiang and co-workers showed a versatile alternative to the in situ preparation of the propargyl vinyl ethers starting from propargylic alcohols and acceptor-substituted alkynes (110BC7313).To this end, cyclic 1,3-diketones 25 and propargylic alcohols 24 were employed, and the corresponding enol ethers were obtained with iron(IIl) tosylate (Scheme 10)... 

Scheme 10 In situ generation of propargyl vinyl ethers and subsequent cyclization.

TL4697, 08SC2607). The propargyl vinyl ethers were then converted with palladium(II) chloride and copper(I) iodide in the presence of tetrabu-tylammonium chloride into bicyclic furans 26 in moderate to good yields. 

---