Thiol catalysts propargylation

Thiol is acting as a co-catalyst in this transformation. In 1997, Alper et al. reported the reaction of thiols, propargyl alcohol, and CO catalyzed by Pd(PPli3)4 (Eq. 7.20)... 

The catalytic propargylic alkylation was investigated in the presence of thiolate-bridged diruthenium complexes as catalysts generated in situ from reactions of [Cp RuCl(p2-Cl)]2 with optically active thiols prepared from the corresponding optically active alcohols [27]. Typical results for the reaction of 1-phenyl-2-propyn-l-ol with acetone in the presence of a variety of catalysts are shovm in Scheme 7.19. 

Substitution reactions of attylic systems. An access to allylic thiols is based on substitution by MeCOSK with (dbaljPdj-dppb as catalyst. 2-Alkylidene-3-alkyl-l,4-benzodioxanes are readily formed in a reaction between catechols and propargylic carbonates. ... 

Nucleophilic Substitution. Aluminum trifluoromethane-sulfonate has been used as a catalyst for the direct nucleophilic substitution of the hydroxyl group of propargylic alcohols (eq 4). The reaction mostly proceeded in very good yields with various nucleophiles such as alcohols, amides, thiols, indoles, and anisole to access highly functionalized alkynes. The catalyst couldbe used in concentrations as low as 0.5 mol % and could be reused up to three times without a significant loss of activity. 

Winnik and coworkers [11] utilized an azide functional RAFT agent to synthesize azide functional linear PNIPAM followed by a thiol-ene Michael addition reaction with propargyl acrylate, producing a-alkyne-ou-azide PNIPAM. Consequently, the cyclization reaction by CuAAC was achieved in water with CUSO4 and ascorbic acid as the catalyst (Scheme 33). Further, the solution properties showed that the cyclic PNIPAM had higher phase transition temperature due to the endless chain structure of the cycUc compared to the linear counterpart with the same molecular weight. 

The thiolate bridged diruthenium complex [(r] -C5Me5)RuCl(jLz-SR)2Ru(/] -C5Me5)Cl] 211, or its derivative with various anions, proved to be a very efficient catalyst for substitution of propargylic alcohols with a number of nucleophiles. The substitution of propargylic alcohols proceeds with heteroatom nucleophiles such as alcohols, thiols, amines, amides, and phosphineoxides to give the corresponding ethers 212, thioethers 213, amines 214, amides 215, and phosphineoxides 216 (Scheme 97) [135]. Carbon nucleophiles such ketones and... 

In the transition-metal-catalyzed Markovnikov-type addition of thiols to terminal alkynes, the double-bond-isomerization reactions of the formed Markovnikov addition products 1 are often observed, when the propargylic protons are present in alkynes. As already mentioned, the addition of amines to the reaction systems suppresses the formation of the double-bond-isomerization product 2. On the other hand, the use of PdCl2(PhCN)2 as a catalyst causes Markovnikov addition of PhSH to terminal alkynes and the following double-bond-isomerization reaction, which afford 2-phenylsulfanyl-2-alkene 2 as the major product (Scheme 15) [7, 48]. 

Furthermore, highly stereoselective dithiocarbonylation of propargylic mesylates with thiols and carbon monoxide is attained by the use of tetrakis(triphenyl-phosphine)palladium(O) as the catalyst. This dithiocarbonylation is believed to proceed via allenylpalladium and allenyl thioesters, and the high stereoselectivity may be rationalized by a mechanism where nucleophilic attack of a Pd(0) species on the... 

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