Carbon-Carbon Bond Construction: The Houk/Qu/Yu Synthesis of Spirooliganin
Yan Qi and Yongjun Liu of the Qingdao University of Science and Technology demonstrated that the assembly of the tertiary alcohol 3 by the Barbier coupling of cyclohexanone 1 with the bromide 2 could be effectively carried out with Sm metal (Chem. Commun. 2021, 57, 6169. DOI: 10.1039/D1CC00965F). Luo Yang of Xiangtan University observed that the hydrocyanation of the alkyne 4 proceeded with high regioselectivity, to give the nitrile 5 (Adv. Synth. Catal. 2021, 363, 283. DOI: 10.1002/adsc.202000935). Philippe Renaud of the University of Bern established conditions for the Giese addition of 7 to the electron-rich enol ether 6, leading to the diester 8 (Chem. Sci. 2021, 12, 2225. DOI: 10.1039/D0SC06341J). Jakob Magolan of McMaster University devised the transpositive assembly of the ketone 11 by the addition of the easily-prepared phosphonium salt 10 to the aldehyde 9, followed by hydrolysis (Org. Lett. 2021, 23, 4548. DOI: 10.1021/acs.orglett.1c01189).
Kui-Ling Ding of the Shanghai Institute of Organic Chemistry and Qi-Lin Zhou of Nankai University also observed high regioselectivity in the hydroformylation of 12 with 13 to give the unsaturated aldehyde 14 (Org. Lett. 2021, 23, 2074. DOI: 10.1021/acs.orglett.1c00234). Mathias Christmann of the Freie Universitšt Berlin found that the addition of LiCl enabled the Fe-catalyzed coupling of the alkyl Grignard reagent 16 with the allylic acetate 15, leading to 17 (Org. Lett. 2021, 23, 4731. DOI: 10.1021/acs.orglett.1c01457). Georg Manolikakes of the TU Kaiserlautern established conditions for the geometrically-controlled construction of the nitro fatty acid 20, by the addition of the nitro ester 18 to the aldehyde 19, followed by dehydration and hydrolysis (Eur. J. Org. Chem. 2021, 2239. DOI: 10.1002/ejoc.202100247). Wei Shu of the Southern University of Science and Technology devised the Ni-catalyzed triply convergent assembly of the enone 21, the alkyne 22 and the bromide 23 to give the conjugate addition product 24 (Nature Commun. 2021, 12, 928. DOI: 10.1038/s41467-021-21083-w).
Wei Deng and Jian-Nan Xiang of Hunan University and Yong-Yue Luo of the Chinese Academy of Tropical Agricultural Sciences established the decarbonylative coupling of the aldehyde 26 with the tertiary propargylic alcohol 25 to give the ketone 27 (Org. Biomol. Chem. 2021, 19, 3154. DOI: 10.1039/D1OB00212K). Pengchen Qian and Jiang Cheng of Wenzhou University reported a closely-related investigation (Org. Biomol. Chem. 2021, 19, 2416. DOI: 10.1039/D1OB00192B). Brian Gold of the University of New Mexico and Ronald T. Raines of MIT described the preparation of the reactive dibenzocyclooctyne 29 by the carbodiimide-mediated dehydration of the tetrazole 28 (J. Am. Chem. Soc. 2021, 143, 9489. DOI: 10.1021/jacs.1c03133).
Min Wang and Jian Liao of the Chengdu Institute of Biology and Lianrui Hu of Xihua University used an enantiomerically-pure sulfoxide to mediate the enantioselective conversion of the enyne 30 to the stannyl allene 31 (Chem. Sci. 2021, 12, 3032. DOI: 10.1039/D0SC05425A). Xin-Yuan Liu, also of the Southern University of Science and Technology, found that a Cinchona-derived Cu complex directed the enantioselective assembly of the allene 35 by the triply-convergent coupling of the enyne 32, the α-bromoester 33, and the alkyne 34 (Angew. Chem. Int. Ed. 2021, 60, 2160. DOI: 10.1002/anie.202013022).
Spirooliganin (39), isolated from the stem bark of Illicium oligandrum, showed effective antiviral activity. Pursuing the synthesis of 39, Kendall N. Houk of UCLA and Jing Qu and Shi-Shan Yu of the Institute of Material Medica prepared the starting enone 38 by coupling the useful linchpin phosphonium salt first with the iodide 37, then with formaldehyde (Chem. Sci. 2021, 12, 7003. DOI: 10.1039/D1SC01277K).