Coupling with propargyl halides

Reaction of Zinc-Copper Couple with Propargyl Halides to Give Allenes... 

Various metal acetylides are used for smooth coupling with propargylic halides and acetates. 2,3-Alkadien-5-yn-l -ols are obtained by the reaction of 2-(l -alkynyl)oxiranes [28,29], As a synthetic application, the unstable 2,3-octadiene-5,7-diyn-l-ol (136), a fungus metabolite, has been synthesized by the coupling of 4-trimethylsilylbutadiy-nylzinc chloride (134) with 2-ethynyloxirane (135) followed by desilylation [31]. 

Allylic and Propargylic Coupling With a Halide Substrate... 

Reaction with Propargyl Halides. The indium-mediated coupling of propargyl bromide with a variety of imines and imine oxides afforded homo-propargylamine derivatives in aqueous media under mild conditions.78 Propargylation of glyoxylic oxime ether in the presence of a catalytic amount of palladium(O) complex and indium(I) iodide in aqueous media was also studied (Eq.11.47).79... 

Allylic and Propargylic Coupling with a Halide Substrate De-halogen-coupling... 

Terminal alkynes couple with propargyl-type halides (45) in the presence of copper(i) chloride and ammonia or an amine . Two types of coupling products have been observed, allenynes 46 and 1,4-diynes 47. When R is hydrogen, the... 

Accordingly, iron-catalyzed coupling of tricyclo[4.1.0.0 ]hept-l-ylmagnesium bromide and related Grignard reagents with propargylic halides proceeds either in an overall Sn- or Sn fashion depending on the substitution pattern of the alkyne (Scheme 4-204). Terminal alkynes predominantly afford allenes via a Sn route, whereas trimethylsilyl-substituted alkynes lead to alkyne derivatives. ... 

Copper(I) halide-catalyzed coupling reactions of perfluoro Gngnard reagents with allyl and propargyl halides have been reported [256], The acetylenic copper compound may be an intermediate in these reactions. 

Likewise, an efficient one-pot multicomponent synthesis of annelated 2-amino pyridines (e.g., 17) utilizing [4+2] cycloadditions has been described <06JOC3494>. The process involves the in situ generation of 1-aza-1,3-butadiene from a palladium-catalyzed coupling-isomerization reaction of aryl halides (e.g., 18) with propargyl V-tosylamines (e.g., 19). The resulting butadiene then undergoes cycloadditions with V.S -ketene acetals (e.g., 20) to form annelated pyridines (e.g., 17). 

Palladium-catalyzed cyclization reactions with aryl halides have been used to synthesize pyrazole derivatives. V-Aryl-lV-(c>-bromobenzyl)hydrazines 26 participated in a palladium-catalyzed intramolecular amination reaction to give 2-aryl-2W-indazoles 27 . Palladium-catalyzed cascade intermolecular queuing-cyclocondensation reaction of o-iodophenol (28) with dimethylallene and aryl hydrazines provided pyrazolyl chromanones 29 <00TL7129>. A novel one-pot synthesis of 3,5-disubstituted-2-pyrazolines 32 has been achieved with an unexpected coupling-isomerization sequence of haloarene 30, propargyl alcohol 31, and methylhydrazine <00ACIE1253>. 

Muller and co-workers reported the three-component one-pot synthesis of various pyrimidines through the in situ generation of unsaturated carbonyl compounds. The palladium catalyzed coupling of aryl halides bearing electron withdrawing substituents 7 with propargyl alcohols 8 produced unsaturated carbonyl compounds 9 after isomerization, which condensed with amidines 10 to form triaryl pyrimidines 11 . 

In the Pd-catalyzed cross-coupling reactions of acylzirconocene chlorides with allylic halides and/or acetates (Section 5.4.4.4), the isolation of the expected p,y-unsaturated ketone is hampered by the formation of the a, P-un saturated ketone, which arises from isomerization of the p,y-double bond. This undesirable formation of the unsaturated ketone can be avoided by the use of a Cu(I) catalyst instead of a Pd catalyst [35], Most Cu(I) salts, with the exception of CuBr - SMe2, can be used as efficient catalysts Thus the reactions of acylzirconocene chlorides with allyl compounds (Table 5 8 and Scheme 5 30) or propargyl halides (Table 5.9) in the presence of a catalytic amount (10 mol%) of Cu(I) in DMF or THF are completed within 1 h at 0°C to give ffie acyl--allyl or acyl-allenyl coupled products, respectively, in good yields. ill... 

Changing to a trisubstituted aromatic precursor such as 1,3,5-tribromobenzene (153) yields the trisallene 155 when l-bromo-2-butyne (154) is used as the coupling partner. When leaving groups of different reactivity are present in the aromatic substrate, such as in l-bromo-4-iodobenzene, different propargyl halides can be connected to the aromatic core, resulting in the formation of arylallenes with different allene substituents. 

Some synthetically important allenylmetallics, such as allenylzinc and allenylin-dium reagents, are prepared from allenylpalladium intermediates. These reactions are discussed in appropriate sections of this chapter. This section covers the reactions of allenylpalladium compounds without further transmetallation. Allenylpalladium complexes can be prepared from propargylic halides, acetates, carbonates, mesylates, alcohols and certain alkynes [83-87], The allenylpalladium compound prepared from 3-chloro-3-methyl-l-butyne has been isolated and characterized spectroscopically (Eq. 9.106) [83], It was found to couple with organozinc chlorides to produce homologated allenes quantitatively (Eq. 9.107). 

CopperiD-Catalysed Coupling or Acetylenes with Allyiic or Propargylic Halides or... 

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