1.3- dicarbonyl compounds reaction with propargylic

The formation of an allenyl ketone as the sole product can be achieved by using an excess (2 equiv.) of propargyl bromide (entries 3—6, Table 5.9). Use of an increased amount (3 equiv.) of the acylzirconocene chloride in the reaction with propargyl bromide and/or tosylate yields a significant amount of a 1,4-dicarbonyl compound derived from Michael-type addition of the acylzirconocene chloride to the initially formed allenyl ketone (entry 2, Table 5.9). The Michael-type addition of acylzirconocene chlorides to allenyl ketones under Cu(I)-catalyzed conditions has been confirmed by an independent experiment (Scheme 5.31). 

The cationic iridium complex [Ir(cod)(PPh3)2]OTf, when activated by H2, catalyzes the aldol reaction of aldehydes 141 or acetal with silyl enol ethers 142 to afford 143 (Equation 10.37) [63]. The same Ir complex catalyzes the coupling of a, 5-enones with silyl enol ethers to give 1,5-dicarbonyl compounds [64]. Furthermore, the alkylation of propargylic esters 144 with silyl enol ethers 145 catalyzed by [Ir(cod)[P(OPh)3]2]OTf gives alkylated products 146 in high yields (Equation 10.38) [65]. An iridium-catalyzed enantioselective reductive aldol reaction has also been reported [66]. 

Related studies have recently been reported by the same author on propargyl steres reactions with dicarbonyl compounds or electron-rich arenes [135], to provide an atom-economical functionalization of carbon nucleophiles under catalytic conditions, using a very different method of addition catalyzed by Lewis acids [136]. 

Propargylation (8, 148-149). The propargylation of aromatics and /1-dicarbonyl compounds with (propargyl)dicobalt hexacarbonyl cations (I) is now used for selective alkylation of ketones and their Irimethylsilyl enol ethers and enol acetates. The reaction is regiospccific and involves attack of the more thermodynamically stable enol, In the case of ketones, yields are substantially reduced by use of a solvent. In the case of enol derivatives, CH2C12 can be used.1... 

The coupling reaction of a-keto esters with allyl, propargyl, and allenyl halides using indium metal in aqueous solvents affords a-hydroxy-y,<5-unsaturated esters (Equation (28)).197,198 1,3-Dicarbonyl compounds undergo efficient carbonyl allylation reactions in an aqueous medium through a Barbier-type reaction (Equation (29)). The reaction is general and a variety of 1,3-dicarbonyls has been alkylated using allyl bromide or allyl chloride in conjunction with indium.199... 

In addition to their reactions with trlmethylsilyl enol ethers, (propargyl1um)Co2(C0)g complexes react with a variety of other mild carbon nucleophiles including activated aromatic compounds, g-dicarbonyl compounds, other enol derivatives (enol acetates and ketones directly), allylsilanes, and alkyl- and alkynyl-aluminum reagents. These reactions provide a flexible means to introduce the synthetically versatile propargyl function. Key features of propargylations using these complexes are 1) ready... 

Attyl and propargyl group transfer. Sulfinic acids or their sodium salts assist Pd(0)-catalyzed deallylation by accepting the allyl group. In addition to allylic esters, allylic sulfoximines can also deliver the allyl group to nucleophiles such as amines. Acrolein acetals react with 1,3-dicarbonyl compounds but the regiochemistry is strongly dependent on reaction temperatures. ... 

Propargyl)Co2(CO)g radicals presumably are also involved in the Mn(III)-mediated addition of P-dicarbonyl compounds to complexed 1,3-enynes, which produces highly functionalized dihydrofiuan derivatives 122 (Scheme 4-65) [222, 223]. The chemo-, regio-, and stereoselectivity of these reactions stands in contrast to the variable selectivity associated with the corresponding reactions of free enynes [224]. The formation of ethers 123 in methanol (Scheme 4-65) suggests that the cobalt-propargyl radicals initially produced are rapidly oxidized by Mn(III) to the stabilized carbocations. 

Dicarbonyl compounds have featured in several approaches to dihydrofurans under a variety of reaction conditions. The palladium-catalysed reaction of propargyl carbonates with ethyl acetoacetate generates 4-methylene-4,5-dihydrofurans (57) in high yield (79-94%) in neutral media but the use of B-diketones leads to... 

Thiolate-bridged dirutheniutn complexes catalyze the [3-f3] cycloaddition reaction between propargylic alcohols and cyclic 1,3-dicarbonyl compounds to afford 4,6,7,8-tetrahydrochromen-5-ones or 4//-cyclopenta[b]pyran-5-ones [193] and with 2-naphthols or phenols to afford l//-naphtho[2,l-b]pyrans and 4//-l-benzo-pyrans, respectively [194]. This cycloaddition is considered to proceed by stepwise propargylation and intramolecular cyclization (carbon and oxygen nucleophile additions) reactions, where ruthenium allenylidene and vinylidene complexes are the key intermediates (Scheme 57). Enantioselective mthenium-catalyzed [3-f3] cycloaddition of propargylic alcohols with 2-naphthols has also been described [195]. 

Roy and coworkers reported that Ir-Sn bimetallic complex serves as efficient catalyst for the synthesis of furans and pyrroles from 1,3-dicarbonyl compounds. This reaction proceeds initial alkylation of 1,3-dicarbonyl compounds with propargyUc alcohol to form propargylated 1,3-dicarbonyl intermediate, followed by ring closure which led to the cyclization products [167]. 

Similar to the reaction with diarylpropene, the use of diarylpropynes enables propargylation of 1,3-dicarbonyl compounds to give 81 (Scheme 8.36). Oxidative C-C bond formations are also possible at the benzylic position in the case of reaction with 1,3-diaryl-l,3-diketones, and allylated and ben-zylated compounds 82 are obtained in moderate yields (Scheme 8.37). ... 

However, when secondary propargyUc alcohols were used as substrates to perform reactions with 1,3-dicarbonyl compounds, tetrasubstituted furans 22 instead of diene-diones were obtained (Scheme 5.11) [17]. In this case, the process combines trifluoroacetic acid-promoted propargylation of 1,3-dicarbonyl compounds and a Ru-catalyzed cycloisomerization of the resulting y-keto alkynes 23. 

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