2018
DOI: 10.1021/acscatal.8b00257
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Copper-Catalyzed Borylative Ring Closing C–C Coupling toward Spiro- and Dispiroheterocycles

Abstract: The synthesis of spiroheterocyclic structures with a pendant methylene boronate substituent has been accomplished to promote further functionalization. A Cucatalyzed borylative ring closing C−C coupling of an alkenyl halide is the key step toward the synthesis of [m.n]-spirocycles (m,n = 3−5). Computational studies on the mechanism reproduced all the experimental trends and explain the enhanced reactivity of systems leading to strained smaller rings. The optimized protocol also gives access to dispirocycle sca… Show more

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Cited by 42 publications
(17 citation statements)
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“…Although Li + does not change the nature of the species, it induces some C−B lengthening (+0.04 Å) and pyramidalization of the carbanionic carbon (−30°), with respect to the free carbanion 1a pin . Note that introducing specific solvation molecules solvating Li + cation [41] would diminish its effect on the electronic structure of borata‐alkene. On the other extreme, the computed C−B bond order of palladium complex 1a pin ‐Pd is close to 1 and the corresponding distance (1.55 Å) is significantly larger than for 1a pin ‐Li .…”
Section: Resultsmentioning
confidence: 99%
“…Although Li + does not change the nature of the species, it induces some C−B lengthening (+0.04 Å) and pyramidalization of the carbanionic carbon (−30°), with respect to the free carbanion 1a pin . Note that introducing specific solvation molecules solvating Li + cation [41] would diminish its effect on the electronic structure of borata‐alkene. On the other extreme, the computed C−B bond order of palladium complex 1a pin ‐Pd is close to 1 and the corresponding distance (1.55 Å) is significantly larger than for 1a pin ‐Li .…”
Section: Resultsmentioning
confidence: 99%
“…However, the high-valent copper(III) species could be a transient species or a transition state of the concerted mechanism. 49,71 Finally, reductive elimination forms the new C−C bond to produce the alkylboration product 4xy with concomitant restoration of copper(I) alkoxide Int1.…”
Section: ■ Results and Discussionmentioning
confidence: 99%
“…This intermediate was transformed to the iodo derivative 38 in a two-step sequence by reduction of the ester function with LiBH 4 to the alcohol followed by the Appel reaction to give the iodoalkene 38 . Finally, iodoalkenes 32 and 38 were transformed toward the desired spirocyclic intermediates 33 and 39 through a copper-catalyzed borylative ring-closing C–C coupling . The Csp 2 –Csp 3 Suzuki cross-coupling reaction between 33 and 39 and 4-bromo-2,6-dimethylpyridine yielded the spirocyclic amines 34 and 40 , which were deprotected in a final step under standard Boc and Bn deprotection reaction conditions (Scheme ).…”
Section: Results and Discussionmentioning
confidence: 99%
“…Subsequent reduction with LiAlH 4 to the alcohol followed by treatment with I 2 in the presence of PPh formed toward the desired spirocyclic intermediates 33 and 39 through a copper-catalyzed borylative ring-closing C−C coupling. 92 The Csp 2 −Csp 3 Suzuki cross-coupling reaction between 33 and 39 and 4-bromo-2,6-dimethylpyridine yielded the spirocyclic amines 34 and 40, which were deprotected in a final step under standard Boc and Bn deprotection reaction conditions (Scheme 3). Intermediates 43 and 45, where the northern heteroaromatic is linked to the spirobicyclic core by an oxygen atom, were prepared from the corresponding alcohols 22 and 26 through an O-alkylation reaction with 4-chloro-or 4-bromo-2,6dimethylpyridine using sodium hydride as the base followed by the cleavage of the Bn and Boc protecting groups, respectively (Scheme 4A,B).…”
Section: ■ Introductionmentioning
confidence: 99%