Carbon-Carbon Bond Formation: The Kalesse Synthesis of Illisimonin A
Biplap Maji of the Indian Institute of Science Education and Research Kolkata prepared the α-hydroxy acid 3 by combining the primary alcohol 1 with ethylene glycol 2 (Angew. Chem. Int. Ed. 2023, 62, e202218329. DOI: 10.1002/anie.202218329). Ramagonolla Kranthikumar of Harvard University assembled the ketone 6 by coupling the thioester 4 with the pyridinium salt 5 (Org. Lett. 2023, 25, 3623. DOI: 10.1021/acs.orglett.3c00943). Yu Kawamata and Phil S. Baran of Scripps/La Jolla established practical conditions for Kolbe electrolysis, illustrated by the cross coupling of the acid 7 with an excess of the acid 8, leading to 9 (Science 2023, 380, 81. DOI: 10.1126/science.adf4762). David W. C. MacMillan of Princeton University devised the Ni catalyzed coupling of the bromide 11 with the secondary alcohol 10 to give 12 (J. Am. Chem. Soc. 2023, 145, 7736. DOI: 10.1021/jacs.3c01488).
Xing-Wei Yang of Sun Yat-sen University optimized the conversion of the β-keto ester 13 to the α-methylene ketone 14 (Chem. Commun. 2023, 59, 6215. DOI: 10.1039/D3CC01268A). Jin-Bao Peng of Wuyi University developed the reductive coupling of the nitroaromatic 16 with the alkenyl cyclopropane 15, leading to the homoallylic amine 17 (Org. Lett. 2023, 25, 2991. DOI: 10.1021/acs.orglett.3c00781). Tao Xu of Tongji University prepared the β-keto phosphonate 20 by coupling the bromophosphonate 19 with the aldehyde 18 (Org. Chem. Front 2023, 10, 3061. DOI: 10.1039/D3QO00543G).
Manuel van Gemmeren of Westfälische Wilhelms-Universität Münster devised a variation on the Ramberg-Bäcklund rearrangement, converting the readily-available bis-sulfone 21 to the alkene 22 (Chem. Eur. J. 2023, 29, e202203512. DOI: 10.1002/chem.202203512).
Narihito Ogawa of Meiji University showed that an allylic phosphonate such as 23 could be coupled with an alkyne 24 to give the eneyne 25 without scrambling the alkene geometry (Eur. J. Org. Chem. 2023, 26, e202300056. DOI: 10.1002/ejoc.202300056). Chao Liu of the Lanzhou Institute of Chemical Physics established a powerful new method for alkyne synthesis, combining the lithiated diborane 27 with the ester 26 to give the alkyne 28 (Nature Synthesis 2023, 2, 413. DOI: 10.1038/s44160-023-00243-4).
Shengming Ma of the Shanghai Institute of Organic Chemistry and Wanbing Zhang of Shanghai Jiao Tong University achieved high enantioselectivity and diasteroselectivity in the preparation of the α-quaternary amine 31 by the alkylation of the protected amino ester 30 with the racemic allene 29 (Angew. Chem. Int. Ed. 2023, 62, e202218146. DOI: 10.1002/anie.202218146). Xueling Mi of Beijing Normal University and Sanzhong Luo of Tsinghua University also achieved high enantioselectivty in the alkylation of the β-keto ester 33 with the eneyne 32 to give the allene 34 (Nature Commun. 2023, 14, 2911. DOI: 10.1038/s41467-023-38488-4).
Illisimonin A (37) was isolated from the poisonous East Asian tree Illicium simonsii. Markus Kalesse of Leibniz Universität Hannover, faced with the challenge of adding a nucleophile to the very congested ketone of 35, solved the problem by cyclizing the chloromethyl silane 35 to the tertiary alcohol 36 (J. Am. Chem. Soc. 2023, 145, 7021. DOI: 10.1021/jacs.3c01262).