Functional Group Interconversion: The Simpkins Synthesis of Concavine
Christian B. W. Stark of the Universität Hamburg found (Org. Biomol. Chem. 2017, 15, 4282. DOI: 10.1039/C7OB00607A) that the Burgess reagent gave particularly high regioselectivity in the dehydration of 1 to 2. Bernhard Hauer of the Universität Stuttgart showed (Nature Chem. Biol. 2017, 13, 275. DOI: 10.1038/nchembio.2271) that linalool dehydratase isomerase derived from Castellaniella defragrans also gave high regioselectivity in the dehydration of a vinyl carbinol 3 to the diene 4. Although the anti-Markovnikov addition of HBr to an alkene 5 to give the terminal bromide 6 is a textbook reaction, it is little used. Hiroshi Matsubara observed (Tetrahedron Lett. 2017, 58, 1190. DOI: 10.1016/j.tetlet.2017.02.020) that HBr in dioxane is a convenient reagent for effecting this transformation. Sandip S. Shinde of the National Chemical Laboratory used (Tetrahedron Lett. 2017, 58, 59. DOI: 10.1016/j.tetlet.2016.11.099) a microcrystalline MoO3 catalyst to promote the conversion of a primary mesylate 7 to the fluoride 8. Xiufang Xu and Pingping Tang of Nankai University converted (Angew. Chem. Int. Ed. 2017, 56, 1101. DOI: 10.1002/anie.201609741) an alkyl silane (not illustrated) to the corresponding fluoride.
Haijun Chen of Fuzhou University demonstrated (Adv. Synth. Catal. 2017, 359, 687. DOI: 10.1002/adsc.201601108) that photooxygenation could cleanly convert a dimethyl aniline 9 to the monomethyl aniline 10. Mitsunobu esterification usually proceeds with inversion of absolute configuration. Radek Cibulka of the University of Chemistry and Technology reported (Org. Biomol. Chem. 2017, 15, 1970. DOI: 10.1039/C6OB02770A) the combination of the alcohol 11 with the acid 12 under photochemical conditions to give ester 13 with retention of absolute configuration.
Hongbin Zhai of the Shenzen Graduate School of Peking University and Yun Li of Lanzhou University devised (Chem. Commun. 2017, 53, 6926. DOI: 10.1039/C7CC03919K) a Co catalyst for the hydration of a terminal alkyne 14 to the methyl ketone 15. Tarek Sammakia of the University of Colorado established (J. Org. Chem. 2017, 82, 3245. DOI: 10.1021/acs.joc.6b02931) that thionyl chloride converted a t-butyl ester 16 to the acid chloride 17. Michael Szostak of Rutgers University found (Org. Lett. 2017, 19, 1614. DOI: 10.1021/acs.orglett.7b00429) that an N-Boc amide 18 could couple directly with a primary amine 19 to give the amide 20. Fengbin Song of Janssen Research & Development used (J. Org. Chem. 2017, 82, 3530. DOI: 10.1021/acs.joc.7b00033) the reagent 22 to convert the acid 21 to the nitrile 23. Jérome Waser of the École Polytechnique Fédérale de Lausanne reported (Chem. Sci. 2017, 8, 1790. DOI: 10.1039/C6SC04907A) an alternative strategy (not illustrated) for converting a carboxylic acid to the corresponding nitrile. Ricardo Lira of Pfizer Global Research and Development coupled (Synlett 2017, 28, 245. DOI: 10.1055/s-0036-1588330) the trichloromethyl carbinol 24 with the amine 25 to give the ester 26.
Youhei Sohma and Motomu Kanai of the University of Tokyo showed (Chem. Commun. 2017, 53, 3311. DOI: 10.1039/C6CC10300F) that Sc(OTf)3 could mediate the specific cleavage of a peptide such as 27 adjacent to a serine or a threonine to give the two (or more) constituent peptides 28 and 29.
En route to concavine (32), Nigel S. Simpkins of the University of Birmingham converted (Chem. Sci. 2017, 8, 3384. DOI: 10.1039/C6SC05627J) the sulfoxide 30 (derived from the corresponding sulfide) to the ketone 31. The intermediate in this transformation was the alkenyl sulfide, not illustrated.
The Jan-Feb issue of the Israel Journal of Chemistry, open access through 2018, has a series of articles on Organic Synthesis: Past, Present and Future, with contributions, among others, from Barry Trost, Mike Krische and George Whitesides.