Propargyl carbonates carbonylation

Carbonylation of propargylic carbonates proceeds under mild neutral conditions (50 °C, I-10 atm) using Pd(OAc)2 and Ph ,P as a catalyst, yielding the 2,3-alkadienoates 18 in good yields[9,10]. The 2.3-alkadienoates isomerize to 2,4-dienoates during the reaction depending on the solvents and reaction time. 2-Decynyl methyl carbonate is converted into methyl 2-heptyl-2,3-butadienoate (19) in 82% yield. 

The allenyl moiety (2,3-aikadienyl system) in the carbonylation products is a reactive system and further reactions such as intramolecular Diels-Alder and ene reactions are possible by introducing another double bond at suitable positions of the starting 2-alkynyl carbonates. For example, the propargylic carbonate 33 which has l,8(or 1.9)-diene-3-yne system undergoes tandem carbonylation and intramolecular Diels-Alder reaction to afford the polycyclic compound 34 under mild conditions (60 C, 1 atm). The use of dppp as ligand is important. One of the double bonds of the allenyl ester behaves as part of the dieneflSj. 

The Pd-catalyzed reaction of propargyl electrophiles with carbon monoxide is a convenient route to allenyl carboxylic acid derivatives. In 1986, Tsuji et al. reported the Pd-catalyzed decarboxylation-carbonylation of propargyl carbonates under a CO at-... 

When the Pd-catalyzed carbonylation of a propargyl carbonate was performed in the presence of an activated methylene or methine pronucleophile, the acylpalla-dium intermediate 38 was trapped by the pronucleophile to give 39 (Scheme 3.24) [59]. 

In 1986, Tsuji et al. developed the palladium(0)-catalyzed alkoxycarbonylation of racemic or achiral propargyl carbonates 128 in an alcohol solvent to afford 131 via carbonylation of 129 to 130 (Scheme 4.35) [55], Palladium(0)-catalyzed alkoxycarbonylation of 134 and isomerization to 136 were key steps for the total synthesis of (-)-kallolide B 138 (Scheme 4.36) [56],... 

Carbonylation of propargyl carbonates bearing an amino group yields lactams. The a-vinylidene /1-lactams 82 are prepared by the carbonylation of 4-benzylamino-2-alkynyl methyl carbonates 81 [20], The best results are obtained by using the cyclic phosphite (4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2,2,2]octane) (83). The lactam formation is carried out in THF or MeCN as solvents at 50 °C under 1-10 atm of CO. 

Diene-A-ynes. Propargylic carbonates in reactions catalyzed by Pd(0) can react as allenyl complexes. Thus carbonylation of 2-alkynyl carbonates catalyzed by Pd(0) results in 2,3-dienylcarboxylates as the major or only product (equation I). Similarly, coupling of 2-alkynyl carbonates with terminal acetylenes in the presence of Cul and LiCl and catalyzed by Pd(0) provides l,2-diene-4-ynes in 60-83% yield (equation II). 

The allenyl esters formed by the carbonylation undergo an intramolecular ene reaction when an olefinic bond exists in a suitable position [12]. A particularly facile ene reaction is observed with these propargyl carbonates having an ester group attached to the triple bond. 

Allylation and propargylation of carbonyl compounds have been surveyed [5]. This section focuses on regio- and stereochemical aspects of the carbonyl allylation reactions in organic and aqueous media. Allylation of carbonyl compounds also proceeds under solvent-free conditions [10] or in liquid carbon dioxide [11]. Allylation with a catalytic amount of indium (0.01-0.1 equiv.) in combination with manganese and chlorotrimethylsilane has been reported [12]. Allylindium reagents have successfully been applied to syntheses of several natural products [13]. 

Allene carboxylates have been synthesized from propargylic carbonates using a palladium-catalysed decarboxylation-carbonylation... 

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