Functional Group Protection: The Murai/Arisawa Synthesis of Ansellone A
John C. Jewett of the University of Arizona demonstrated that the protected diazonium salt 1 participated efficiently in Suzuki coupling, leading the biphenyl 2 (Org. Lett. 2021, 23, 1851. ). Takamitsu Hosoya of the Tokyo Medical and Dental University and Suguru Yoshida of the Tokyo University of Science showed that the aryl azide of 3 could be protected in the presence of the alkyl azide, to give 4 (Chem. Commun. 2021, 57, 6062. ).
Keith R. Fandrick and Suttipol Radomkit of Boehringer-Ingelheim used the reagent 6 and a bis(trifluoromethane)sulfonimide/2,6-lutidine catalyst to convert the phenol 5 into the t-butyl ether 7 (J. Org. Chem. 2021, 86, 4877. ). Jie Zhao of the East China University of Science and Technology, Dingsheng Wang of Tsinghua University and F. Dean Toste of the University of California, Berkeley showed that with an Ir catalyst, the benzyl alcohol of 8 could be coupled with the diazo ester 9 to give 10, leaving the phenol unreacted (Nature Catal. 2021, 4, 523. ). Bartholomäus Pieber of the Max Planck Institute of Colloids and Interfaces and Peter H. Seeberger of that institution and the Freie Universität Berlin devised oxidative conditions promoted by long-wavelength visible light to prepare the free alcohol 12 from the benzyl ether 11 (Org. Lett. 2021, 23, 514. ). Ryosuke Matsubara of Kobe University showed that 14 and a carbazole photocatalyst mediated the cleavage of the aryl ether 13 to the phenol 15 (J. Org. Chem. 2021, 86, 2545. ). The protocol cleaved long chain alkyl aryl ethers.
Chi Wai Cheung and Jun-An Ma of Tianjin University showed showed that a primary amine 17 could be acylated with a tertiary amide 16, leading to the secondary amide 18 (ACS Catal. 2021, 11, 7070. ). Ying Fu and Zhengyin Du of Northwest Normal University developed photochemical conditions for converting the benzyl amine 19 to the sulfonamide 20 (Eur. J. Org. Chem. 2021, 1896. ). Jianjun Cheng of the University of Illinois removed the t-butyl group from the urea 21 to give the urea 22 (Chem. Commun. 2021, 57, 3812. ). Chun Hu of Shenyang Pharmaceutical University and Dong-Yu Wang of Shanghai Jiao Tong University combined chlorosulfonyl isocyanate 24 with tBuOH, then pyridine, to form a reagent that converted the amine 23 to the protected sulfamide 25 (Org. Lett. 2021, 23, 2595. ).
On deprotection, 26 tends to form the internal acetal. Shivajirao L. Gholap of the Indian Institute of Technology Delhi developed conditions that delivered the aldehyde 27 (Org. Biomol. Chem. 2021, 19, 1100. ). Fan Chen and Xing-Guo Zhang of Wenzhou University showed that the benzothiazole 28 could be converted into the amide 29 (Chem. Commun. 2021, 57, 1923. ).
Ansellone A (33), isolated from the dorid nudibranch Cadlina luteomarginata, has activity as an HIV latency-reversing agent. In the course of a synthesis of 33, Kenichi Murai and Mitsuhiro Arisawa of Osaka University demonstrated that the alkenyl triflate 30 participated more efficiently in the coupling with 31 to give 32 than did the corresponding alkene (Org. Lett. 2021, 23, 1720. ).