Palladium-catalyzed decarboxylative

The next task was removal of the C3,C3 -esters. Although the palladium-catalyzed decarboxylation protocol performed well in previous systems, a competing C-H insertion reaction was discovered with the methylidene bridge needed for cercosporin (see below). Since reexamination of alternate decarboxylation methods [48] led to no success, a decarbonylation strategy was explored [49]. Formation of the requisite dialdehyde was best accomplished by overreduction using DIB AL and... 

Bisacid 91 was used toward three different targets. For the first, a palladium-catalyzed decarboxylative Heck reaction followed by perylenequinone formation provided bis-styryl derivative 92 (Scheme 7.22) [52]. For the second, the C5,C5 -benzyl ethers were cleaved, and the more acidic carboxylic acids were then selectively benzylated using BnBr and K2CO3 (Scheme 7.22). This re-esterification... 

Several examples of transition metal catalysis for the synthesis of piperidines appeared this year. Palladium catalyzed intramolecular urethane cyclization onto an unactivated allylic alcohol was described as the key step in the stereoselective synthesis of the azasugar 1-deoxymannojirimycin . A new synthetic entry into the 2-azabicyclo[3.3.1]nonane framework was accomplished through a palladium mediated intramolecular coupling of amine tethered vinyl halides and ketone enolates in moderate yields . A palladium catalyzed decarboxylative carbonylation of 5-vinyl... 

Allylic carbonates show high reactivity in a related palladium catalyzed decarboxylative allylation of active methylene compounds (equation II). In this case,... 

Tanaka T, Okamura N et al (1986) Syntheses of (5E)-PGE2 and new 6-functionalized derivatives by the use of palladium-catalyzed decarboxylative allylic alkylation. Tetrahedron 42 6747-6758... 

Oxazolidines can be converted into 3,6-dihydro-177-pyridin-2-ones in a new synthesis (Equation 191) <2000JA2944> involving a palladium-catalyzed decarboxylative carbonylation. 

The palladium-catalyzed decarboxylative coupling of allyl 2-(benzo[c(jthiazol-2-yl)acetates 118 provides a facile approach to 2-(but-3-enyl)benzo[c(jthiazoles 122 <07JA4138>. The reaction is initiated by nucleophilic attack of Pd(0) on the allyl ester to give Pd-7t-allyl complex 119, which undergoes nucleophilic attack at the less substituted allylic carbon from the benzothiazole nitrogen to produce 120. Decarboxylative dearomatization leads to intermediate 121, and a subsequent aza-Cope rearrangement driven by rearomatization affords the final product 122 and accounts for the unusual regioselectivity. This appears to be the first report of a tandem allylation/aza-Cope reaction driven by decarboxylative dearomatization/ rearomatization. 

A six-membered cyclic allylic carbonate 102 undergoes a palladium-catalyzed decarboxylative C-C bond cleavage to afford dienic carbonyl compound 104 [122]. Decarboxylation of the allylic carbonate moiety provides the driving force for production of the intermediate five-membered hetero-palladacycle 103, from which formal reductive cleavage takes place. 

The experimental results that both branched and linear allylic ethers are obtained in the palladium-catalyzed decarboxylation of branched allylic carbonate indicate occurrence of direct oxidative addition involving the C-0 bond cleavage followed by the nucleophilic attack of the alkoxide liberated on either the substituted or non-substituted terminus of the allylic ligand (Scheme 4) [1]. 

A new method of synthesis of multisubstituted nipecotic acid (piperidine-3-carboxylic acid) derivatives (487) has been developed by way of palladium-catalyzed decarboxylative cyclization of y-methylidene-5-valero-lactones (485) with imines (486) (Scheme 124). ... 

Other heterocycles were employed for the synthesis of imidazoles. Reaction of various amines with oxazoles 73 led to an expedient synthesis of imidazoles 74 under microwave conditions (14CC1867). Palladium-catalyzed decarboxylative intramolecular condensation of 1,2,4-oxadiazol-5-(4fJ)-ones 75 furnished substituted imidazoles 76 in good-to-excellent yields (14SL1916). 

In 2000, a palladium-catalyzed decarboxylative carbonylation of 5-vinyloxazolidin-2-ones was studied by Knight and coworkers [44]. By a palladium-catalyzed decarboxylative carbonylation process, 5-vinyloxazohdin-2-ones, which are prepared... 

SCHEME 22.10 Palladium-catalyzed decarboxylative 1,2-addition of carboxylic acids to aldehydes or imines. 

Xiang, S., Cai, S., Zeng, J., Liu, X.-W. (2011). Regio- and stereoselective synthesis of 2-deoxy-C-aryl glycosides via palladium catalyzed decarboxylative reactions. Organic Letters, 13, 4608-4611. 

Luo,Y., Wu, J. (2010). Palladium-catalyzed decarboxylative 1,2-addition of carboxylic acids to aldehydes or imines. Chemical Communications, 46, 3785—3787. 

Voutchkova, A., Coplin, A., Leadbeater, N. E., Crabtree, R. H. (2008). Palladium-catalyzed decarboxylative coupling of aromatic acids with aryl halides or unactivated arenes using microwave heating. Chemical... 

Scheme 3.5 Palladium-catalyzed decarboxylative biaryl synthesis and its putative mechanism, as described by Liu and coworkers [15],...

Very recently, Tan and coworkers [20] reported the synthesis of unsymmetrical biaryls via palladium-catalyzed decarboxylative coupling between aryl carboxylic acids and phenylboronic acids. Under the optimized conditions, where the choice of solvent was found to be crucial for achieving a straightforward and simple coupling reaction, a variety of substituted benzoic acids were found to undergo decarboxylative coupling with several phenylboronic acids (Scheme 3.8). Despite poor substrate scope, this method could be useful and complementary to the Pd-catalyzed... 

Scheme 3.10 Palladium-catalyzed decarboxylative atylation of coumarin-3-carboxylic acids with aryl iodides, as described by Jafarpour and coworkers [22].

Scheme 3.11 Proposed mechanism for the palladium-catalyzed decarboxylative biaryl synthesis, as described by Xie and coworkers [23],...

Scheme 3.13 Palladium-catalyzed decarboxylative C-H bond arylation of thiophenes, as described by Su and coworkers [26].

In 2013, Satoh, Miura, and coworkers [39] reported the palladium-catalyzed decarboxylative ary-lation of readily available 3-benzoylacrylic acids with arylboronic acids in the presence of a copper salt oxidant, affording chalcone derivatives (Scheme 3.22). The decarboxylative arylation could also be achieved using aryl halides as an alternative aryl source (Scheme 3.22). 

Scheme 3.22 Palladium-catalyzed decarboxylative arylation of benzoylacrylic acids for the synthesis of...

As mentioned earlier, we reported the first allylic decarboxylation reaction of pentadienyl esters. We considered that the pentadienyl group was assisting with reactivity, so it was believed that the palladium-catalyzed decarboxylation of diester 73 would be as successful as the previous example. Interestingly, when saturated diester 73 was subjected to the same... 

The palladium-catalyzed decarboxylative coupling of potassium pentafluoroben-zoate with aryl chlorides, bromides and triflates was shown to be a useful method for the synthesis of polyfluorobiaryls from readily accessible polyfluorobenzoate salts. For instance, 2- and 3-chlorothiophens 218, 219 reacted with potassium pentafluorobenzoate to produce pentafluorophenyl derivatives 210 and 220. The reaction proceeded in refluxed diglyme in the presence palladium acetate(ll) [111],... 

Shintani, R., Hayashi, S.-Y., Murakami, M., Takeda, M., Hayashi, T. (2009). Stereoselective synthesis of spirooxindoles by palladium-catalyzed decarboxylative cyclization of Y-methylidene-5-valerolactones with isatins. Organic Letters, 11, 3754-3756. 

Xu, Z., Wang, Q., Zhu, J. (2013). Palladium-catalyzed decarboxylative vinylation of potassium nitrophenyl acetate application to the total synthesis of (—)-goniomitine. Angewandte Chemie International Edition, 46, 3272-3276. 

A conjugated oligomer is synthesized through the palladium-catalyzed decarboxylative coupling of pyrrole-2,5-dicarboxylic acid derivatives with dibromoarenes (Scheme 4.45) [50]. 

It has been reported that a retro-oxidative cyclization process proceeds in catalytic C-C bond cleavage reactions. For example, a six-membered cyclic allylic carbonate 38 underwent a palladium-catalyzed decarboxylative C-C bond cleaving reaction to afford dienyl aldehyde 40 (Scheme 7.12) [15]. It is proposed that oxidative addition of the allylic carbonate to palladium(O) followed by elimination of carbon dioxide generates the palladacycle 39. Subsequent retro-oxidative cyclization produces the diene and aldehyde functionalities. 

Allyl /3-keto carboxylates and allyl enol carbonates undergo a palladium-catalyzed decarboxylation-dehydrogenation to yield o, S-unsaturated ketones in usually high chemical yield and with good selectivity. Following this approach, it was possible to obtain 2-methyl-2-cyclopentenone in two steps from diallyl adipate in a procedure that could be convenient for large-scale preparations (eq 62). ... 

Scheme 5.30 Mechanistic pathways in the palladium-catalyzed decarboxylative allylic alkylation, starting from allyl p-keto esters 91 or allyl enol carbonates 92.

---