Propargylic vinylic

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). 

A very unusual Nazarov cyclization of propargyl vinyl ketones has been reported by Hashmi et al. (Eq. 13.16) [18]. Propargyl alcohol 50 was oxidized to ketone 51 with the Dess-Martin periodinane. Attempts to purify 51 by column chromatography on silica gel led to cyclopentenone 53 in 59% isolated yield. This suggests that the solid support catalyzed the isomerization of 51 to allenyl vinyl ketone 52, which was not isolated, but which underwent spontaneous cyclization to 53. This result is consistent with earlier observations of the great ease with which allenyl vinyl ketones undergo the Nazarov reaction (cf. 8, Eq. 13.2). 

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]... 

Propynyl Vinyl Sulfide (or Propargyl vinyl sulfide). HC = C.CH2.S.CH CH2 mw 98.17 colorl liq bp 28° at 10mm RI 1.5183. Sol in pentane. Prepn is by reacting Na ethyl vinyl sulfide with propynyl bromide in pentane at 0° and then dstlg off the pentane solvent under vac at 20—25°. The residual is then redistld to remove the sulfide at 28°/10mm. The yield is 88—93%. Expl decompn occurs above 80° Refs 1) Beil, not found 2) L. Brandsma, Preparative Acetylenic Chemistry , Elsevier, NY (1971), 7 181... 

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... 

C. Coupling of Terminal Alkynes with Propargyl, Vinyl and Allenyl Halides... 

C=CHCH2NAtN=CR has been reported. " Propargylic vinylic compounds give allenic aldehydes, ketones, esters, or amides ... 

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. 

Allenyl-, Propargyl-, Vinyl- andEthynyl-silanes and -stannanes... 

Similar strategies have been used to develop inhibitors that target the C-18 hydroxylation involved in the biosynthesis of aldosterone . Thus, aldosterone analogs with C-18 iodomethyl, chloromethyl, allyl, propargyl, vinyl, and methyl-thiomethyl functionalities have been synthesized and some have been found to irreversibly inactivate the enzyme. An active site-directed 18-acetylenic deoxycorticosterone [21 -hydroxy-13(-2-)propy-... 

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