Propargyl groups

The (TMS)3Si radical addition to terminal alkenes or alkynes, followed by radical cyclization to oxime ethers, were also studied (Reaction 50). The radical reactions proceeded effectively by the use of triethylborane as a radical initiator to provide the functionalized pyrrolidines via a carbon-carbon bond-forming process. Yields of 79 and 63% are obtained for oxime ethers connected with an olefin or propargyl group, respectively. 

Replacement of the ethanolamine head group is also well tolerated. Substitution with a cyclopropyl (243) [37], allyl (244) or propargyl group (245) [164] all led to an increase in binding affinity compared to AEA. Replacement of the head group with aromatics is also allowed. The phenyl derivative (246) retains affinity at the CBi receptor [37], whereas the 2-substituted A-methyl pyrrole (247) has a 2-fold improved affinity compared to AEA [167]. Interestingly, the 3-substituted furan derivative (23) that has micromolar affinity for the AEA transporter (see above) does not bind to the CBi receptor, but has good affinity for the CB2 receptor [167]. These results are summarised in Table 6.20. 

Arylamines with a propargyl group react under the same conditions [191, 253-256] in the case of the vinylogous amide 108, potassium hydroxide and a phase-transfer catalyst are sufficient [257] (Scheme 1.47). 

M.G. Finn of Scripps/La Jolla has explored (Organic Lett. 2004,6,2777) propargyl protection for phenols. The propargyl ether is removed by BBr, more easily than the usually-labile methyl ether. The propargyl group is removed from a primary alcohol under comparable conditions. 

Alkynylvanadium(III) chloride, 219 Chromium(II) chloride, 84 Lithium methoxyacetylide, 166 Organocerium reagents, 206 Titanium(IV) chloride, 304 Propargyl groups... 

Direct conversion of 10-propargylAP (45Id) to (694) was unsuccessful due to the lability of the propargyl group under the requisite deamination conditions [284,285],... 

Propargylic groups are also known to participate in [2,3]-sigmatropic rearrangements and lead to the isolation of allenes as the major products. For example, the nitrogen ylide 65 was formed by treating the corresponding ammonium salt with NaH in DMSO afforded allene 66 in 86%... 

Actually, an attempt to introduce a propargyl group on phenothiazine in the presence of sodium hydride led fortuitously to the first ynamine synthesis (62) 109). 

Figure 15. Oxidation of amides and influence of neighboring propargyl groups.

In the simplest of these, jS-enaminones are synthesized (equation 129) by the addition of amines to 1,3-diketones or /3-ketoesters. The reaction has been apphed to the Friedlander synthesis of quinolines by condensation of the enaminone and other carbonyl present in the substrate. Substituted pyrroles in equation (130) can be obtained as well when a propargyl group is present, by addition of the enaminone to the triple bond. Alcohols, thiols, and secondary phosphines have been also tested as nucleophiles with good results. A particularly interesting case is found in the condensation of indoles with 1,3-diketones to give substituted indol derivatives in equation (131). ... 

When one of the substituents on sulfur in (3) is an ally or a propargyl group, a thio-Claisen rearrangement is observed (4 - 5). 

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