Unprotected propargyl

The novel heliannane-type sesquiterpenoid (-)-heliannuol E was synthesized in the laboratory of K. Shishido. Interest in the total synthesis of this natural product was not only spurred by its irregular terpenoid structure and significant biological activity but the need to establish the absolute stereochemistry at the C2 and C4 stereocenters. The Sonogashira reaction was utilized to prepare the 3-arylpropargyl alcohol by coupling of a heavily substituted aryl iodide with an unprotected propargyl alcohol in quantitative yield. 

In 2009, Mamidyala and Finn showed that alkynophilic activation by Au(III) is practical for the reaction of unprotected propargyl glycosyl donors 38 with sugar aglycones to produce corresponding disaccharides 39 without significant stereoselectivity (Scheme 8). ... 

Coupling of excess (Z)-l,2-dichloroethene (217) with propargyl alcohol first led to the enyne 218, which, when subjected to a second Pd-catalyzed coupling step with trimethylsilylacetylene, provided the mixed diacetylene 219. With all carbon atoms assembled, the allene function was generated by first producing the (unprotected) hydrazine derivative 220, which on treatment with either diethyl azodicarboxylate (DEAD) or 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) under anaerobic conditions at 0 °C yielded the hydrocarbon 27. According to mechanistic studies, the latter process leads first to a mixture of ( )- and (Z)-diazenes. Sigmatropic elimination of... 

Monomers with unprotected alkyne groups in the side chain cannot be polymerized without side reactions, as the alkylidene catalyst will engage in a competing alkyne metathesis. This side reaction can be avoided by using monomers with alkyne groups either complexed with di-cobalt octacarbonyl 1 or TMS-protected 2 (Scheme 9.3a,b) [14, 35, 36]. Alkyne incorporation at the chain end was achieved in a post-functionalization approach, reacting hydroxyl-terminated polynorbornene (PNBE) 5 with propargylic acid 6 (Scheme 9.3c) [37]. 

The lithium enolate 163 reacts with allylic or propargylic halides to afford precursors to the rra 5-prostanoid ll-deoxy-PGE2 along with its 8,12-epimer in a combined yield of 30% (Scheme 1-118). However, base-catalyzed regiochemical randomization and subsequent P-elimination of any unprotected 11-hydroxy group can often not be prevented. ... 

Brimble and co-workers have demonstrated the synthesis of a stable triazolylalanine analogue of phosphohistidine (632) using the click phosphorylation of a propargylated unprotected peptide (630) and phosphoryl azide (631), catalysed by Cu(I) (Scheme 155). ° ... 

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