Propargyl substitution

An efficient method for the synthesis of IV Group metals substituted indolizines from diverse propargyl-substituted pyridines in the presence of Au-catalyst, has been developed <2006JA12050>. 

The last question still open addresses the alkynyl ketones. The reaction of 64 shows an example with a potential intramolecular competition and here it is possible to isomerize the propargyl substitutent on the ketone quantitatively without changing the 1-hexynyl substituent on the other side [125] (Scheme 1.28). From the publication it is not clear whether the isomerization is really a thermal reaction or occurs during the workup of the thermolysis reaction, for example by chromatography (compare the discussion above [110]). 

Propargylic substitution reaction is one of the most important routes to allenic compounds [1, 2], As shown in Scheme 3.1, replacement of a leaving group at the propargylic position with an incoming nucleophile via an SN2 pathway rearranges the C=C-C skeleton into a C=C=C moiety to give a propadienyl species. With certain... 

As appropriate model compounds for these reactions240 the bridgehead substituted di hydro-4-methyleneazulenes 474 were employed. Allyl-, crotyl- and propargyl-substituted dihydroazulenes 474 and 476 can be easily rearranged to the 4-substituted azulenes 475 and 477 (equations 179 and 180) whereas all attempts to obtain 4-benzylazulene 479 by rearrangement of precursor 478 gave only polymeric products (equation 181). Undoubtedly, this failure can be explained by the fact that the Cope rearrangement becomes very... 

Scheme 20 [Ru( j -C9H7)(PPh3)2] -mediated propargylic substitution of alkynols...

Scheme 39 Propargylic substitution reactions catalyzed by complex 105a...

Scheme 40 Proposed catalytic cycle for the Ru-catalyzed propargylic substitution reactions...

Scheme 41 Propargylic substitution reactions with enolizable ketones...

Fig. 21 Products obtained through propargylic substitution reactions with carbon-centred nucleophiles...

Although no experimental evidences have been furnished, involvement of copper alleny-lidenes in catalytic propargylic substitution processes has been recently proposed Detz RJ, Delville MME, Hiemstra H, van Maarseveen JH (2008) Angew Chem Int Ed 47 3777-3780... 

Taking advantage of the regioselectivity shown by the indenyl-ruthenium(II) complexes [Ru(q -C9H7)(=C=C=CR R )(PPh3)2][PF6] an efficient synthetic procedure for the propargylic substitution of 2-propyn-l-ols mediated by the metallic... 

Propargylic Substitution Reactions with Heteroatom-Centered Nucleophiles... 

In the presence of a catalytic amount of methanethiolate-bridged diruthenium complex (la abbreviated as met-DIRUX), reactions of propargylic alcohols (2) with a variety of heteroatom-centered nucleophiles such as alcohols, thiols, amines, amides, and diphenylphosphine oxide gave the corresponding propargylic substituted... 

Scheme 7.5 Propargylic substitution reactions of propargylic alcohols with a variety of heteroatom-centered nucleophiles.

Diphenylphosphine oxide can be used as a phosphorus-centered nucleophile for propargylic substitution reactions, where its tautomer (diphenylphosphinous acid) is... 

Scheme 7.9 Propargylic substitution reaction with acetone as a carbon-centered nucleophile.

Scheme 7.10 Propargylic substitution reactions with unsymmetrical simple ketones.

---