Organocatalyzed C-C Ring Construction: The List Synthesis of 2-epi-ziza-6(13)-en-3-one
Gullapalli Kumaraswamy of the Indian Institute of Chemical Technology assembled the cyclopropane 3 by the (DHQD) Pyr-mediated addition of the bromo amide 2 to the enone 1 (Tetrahedron 2021, 87, 132110. ). José Alemán of the Universidad Autónoma de Madrid showed that a bis-naphthyl-1,2-diamine mediated the photocyclization of the diene 4, leading to the cyclobutane 5 (Chem. Commun. 2021, 57, 3046. ).
Fu-She Han of the Changchun Institute of Applied Chemistry used a P-stereogenic phosphinamide to direct the reduction of the prochiral diketone 6 to the keto alcohol 7 (J. Am. Chem. Soc. 2021, 143, 2994. ). Manabu Hatano of Kobe Pharmaceutical University and Kazuaki Ishihara of Nagoya University used a BINOL-derived phosphoric acid to mediate the cyclization of the aldehyde 8 to the protected 1,3-diol 9 (ACS Catal. 2021, 11, 6121. ). Takashi Ooi, also of Nagoya University, demonstrated that a racemic Ir photocatalyst complexed with a BINOL-derived chiral borate effectively catalyzed the opening of the cyclopropylamine 10 and subsequent addition to the methacrylate 11, leading to the cyclopentanecarboxylate 12 (Org. Biomol. Chem. 2021, 19, 1744. ). Shuang Yang and Xinqiang Fang of the University of the Chinese Academy of Sciences, Fuzhou, and Jinggong Liu and Bolai Chen of the Guangdong Provincial Hospital of Traditional Chinese Medicine employed an NHC catalyst to combine the aldehyde 13 with the 1,2-diketone 14, to give the cyclopentenone 15 (Org. Lett. 2021, 23, 3403. ).
Jian-Liang Ye and Pei-Qiang Huang of Xiamen University used a thiourea-primary amine catalyst to effect the conjugate addition of nitromethane to the cyclohexenone 16, leading to the ester 17 (Tetrahedron 2021, 84, 132005. ). Stephen G. Pyne of the University of Wollongong assembled the cyclohexane 20 by combining the allyl silane 19 with the tertiary alcohol 18 (Org. Biomol. Chem. 2021, 19, 259. ). Ying-Chun Chen of Sichuan University showed that a modified Jřrgenson-Hayashi catalyst effectively directed the addition of the bis nitrile 22 to the unsaturated aldehyde 21, leading to the cyclohexenecarboxaldehyde 23 (Org. Biomol. Chem. 2021, 19, 151. ). Bernhard Hauer of the University of Stuttgart devised a modified terpene cyclase that converted the ketone 24 to the cyclohexane 25 (Angew. Chem. Int. Ed. 2021, 60, 13251. ).
Ping Lu of Fudan University used a chiral oxazaborolidinium ion to catayze the Diels-Alder cycloaddition of the cyclobutenone 26 to the diene 27, leading to the bicyclic ketone 28 (Angew. Chem. Int. Ed. 2021, 60, 4609. ). Shuanhu Gao of East China Normal University showed that the Jřrgenson-Hayashi catalyst cyclized the prochiral cyclohexadienone 29 to the bicyclic enone 30 (Chem. Sci. 2021, 12, 4747. ).
Vetiver oil, obtained by hydrodistillation of the dried roots of the tufted perennial grass Chrysopogon zizanioides, is omnipresent in perfumery. Philip Kraft of Givaudan and Benjamin List of the Max-Planck-Institut für Kohlenforschung demonstrated by total synthesis, beginning with the imidodiphosphorimidate-catalyzed enantioselective conjugate addition of the ketene silyl acetal 32 to cyclopentenone 31 to give 33, that the lead fragrance contributor of the oil is 2-epi-ziza-6(13)-en-3-one (34), a minor component (Angew. Chem. Int. Ed. 2021, 60, 5666. ).