Propargyl bromide, coupling

Propanol, 1,3-bis(methylthio)-, 54, 19 Propargyl bromide, coupling with an organocopper reagent, 50, 98... 

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... 

Another recent development in the field of palladium-catalyzed reactions with alkynes is a novel multicomponent approach devised by the Lee group. Starting from a-bromovinyl arenes and propargyl bromides, the assembly ofeight-membered car-bocycles can be realized via a cross-coupling/[4+4] cycloaddition reaction. The authors also presented the combination of a cross-coupling and homo [4+2], hetero [4+2], hetero [4+4] or [4+4+1] annulation leading to various cyclic products [147]. 

The classical examples of these two routes are the conversion of 2,5-dimethyl-2,4-hexadiene (113) via the bisdibromocarbene adduct 114 into the terminally fully methylated bisallene 115 (Scheme 5.15) [43] and the reductive coupling of propargyl bromide (116). 

Among the more exotic cydopropylallenes, the polycyclic hydrocarbons 148 (n= 2, 3) may be cited, which are available by coupling the Grignard reagents 147 with propargyl bromide (116) in the presence of various metal catalysts, Fe(acac)3 leading to the highest yields (Scheme 5.21) [60]. 

In an indium-mediated process, the aromatic substrates 150 (X=Br, I, OTf) can be coupled in the presence of catalytic amounts of a Pd° catalyst with the propargyl bromides 151 to yield the arylallenes 152, the reaction most likely proceeding via an allenylindium intermediate (Scheme 5.22) [62],... 

Propargylallene (l,2-hexadien-5-yne) (23) is the other main product obtained when the allenyl copper reagent 117 is coupled with propargyl bromide (116 see above) (Scheme 5.36) [44, 94]. 

Later, a similar coupling reaction between allyl bromide or cinnamyl bromide with Ar3Bi was reported to provide the coupling products in good yields when the bromides were used in excess (Scheme 50) [65]. Under the same reaction conditions, arylation of propargyl bromide also proceeded to provide arylated allenes in moderate yields (Scheme 51) [65]. 

Scheme 51 Cross-coupling reaction of Ar3Bi with propargyl bromide...

Coupling of Propargyl Bromide with (he Grignard Derivative of the O-Protected Propargyl Alcohol in the Presence of Copper(I)Chloride. Synthesis or 2 -Pentadiyn-l-ol... 

A unique reaction of allenylindium reagents, prepared from propargyl bromides and indium, and haloazines gives rise to the appropriate allenyl-azines. Although the reaction is not a Heck coupling, but a cross-coupling reaction, the aryl moiety is formally attached to a carbon-carbon multiple bond, therefore we mention it here. 

Bromopyrimidine and l-bromo-2-butyne reacted to give the butadienyl-pyrimidine derivative in 92% yield, while the sequential coupling of propargyl bromide and l-bromo-2-butyne with 2,5-dibromopyridine gave the expected product in 65% (7.59.), the first allene moiety being introduced into the more reactive 2-position, and the second allene attached to position... 

Usanov and Yamamoto recently found that catalytic amounts of Co(TPP) 367 led to a dramatic rate acceleration of Nozaki-Kishi-Hiyama reactions catalyzed by chromium complex 368 (Fig. 101) [460]. The authors attributed the rate enhancement to initial reduction of 367 to a Co(I) complex. The latter is able to undergo an Sn2 substitution at propargyl bromide 366 giving an allenylCo(ffl) species. It was proposed that its homolysis leads to allenyl radical 366A, which couples to Cr(II) complex 368. The resulting allenyl Cr(III) complex adds in an SN2 process... 

The indium-catalyzed coupling of propargyl bromide with a variety of imines and nitrile A-oxides affords the corresponding propargylated products in high yields under mild conditions (Scheme 64).261... 

Allenylindium reagents, generated in situ from the reaction of indium with propargyl bromides, can be employed as effective cross-coupling partners in palladium-catalyzed reactions with a variety of organic electrophiles to produce substituted allenes, polyallenes, unsymmetrical bisallenes in excellent yields (Table 22).358... 

Suitable cleaving agents include organic halides such as primary alkyl bromides, iodides or sulfo-nates " ° allylic," - allenic and propargylic bromides vinylic or aryl halides with nickel or palladium promoters " alkyl chloroformates epoxides and even cyanogen or cyanogen bromide. Typical examples of such couplings are depicted in equations (55)-(57). 

We protect one hydroxyl terminus of the commercially available 1,8-octane diol 1 by reaction with dihydropyran to give the monoalcohol, 8-tetrahydropyranyloxyoctanol 2. The protected alcohol 2 is oxidized to the aldehyde with pyridinium chlorochromate to give 8-tetrahydropyranyl-oxyoctanal 3. 1-Heptyne 4 is coupled with propargyl bromide 5 in a copper catalyzed reaction to produce the diacetylenic 1,4-decadiyne 6. 

An extension of Tsuji s methodology has recently been reported by Liang in which he is able to perform a three-component coupling for the preparation of tetrasubstituted furans [154]. A combination of methyl or ethyl acetoacetate with propargyl bromide or carbonate and an aryl iodide enables the formation of tetrasubstituted furans 184. The proposed mechanism for this transformation is similar to that of Tsuji in that an allenyl-palladium intermediate is postulated. However, a three-component reaction is possible because the initial oxidative addition in this reaction is with the aryl iodide. Interaction of this Pd(II) intermediate with the propargyl bromide or carbonate leads to the allenyl-palladium species and, eventually, the product 184. 

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