Carbon-carbon bond construction: The Hulme synthesis of Disorazole C₁

Keiichi Hirano and Masanobu Uchiyama of the University of Tokyo converted (Chem. Asian J. 2015, 10, 1286. DOI: 10.1002/asia.201500308) the acid 1 to the methyl ketone 3 using the zincate 2. Exposure (J. Org. Chem. 2005, 70, 6417. DOI: 10.1021/jo0508752) of an ester to the Petasis reagent will effect the same transformation. Zheng Huang of the Shanghai Institute of Organic Chemistry effected (Angew. Chem. Int. Ed. 2015, 54, 4023. DOI: 10.1002/anie.201410293) the borrowed hydrogen condensation of the ester 5 with the alcohol 4 to give 6. Alfonso Fernández-Mateos of the Universidad de Salamanca showed (Eur. J. Org. Chem. 2015, 548. DOI: 10.1002/ejoc.201403288) that the alcohol 9 could be constructed by using the vinyl sulfone 8 as the acceptor for the radical formed by reductive opening of the epoxide 7. Ohyun Kwon of UCLA took advantage (Org. Lett. 2015, 17, 1054. DOI: 10.1021/acs.orglett.5b00209) of the accelerating effect of halogen for the Claisen rearrangement to 11 of the ketene acetal derived from the readily-prepared 10.

Yan-Biao Kang of the University of Science and Technology of China condensed (Chem. Commun. 2015, 51, 7729. DOI: 10.1039/C5CC01965F) the sulfone 12 with the alcohol 11 to give the alkene 13. In related work, David Milstein of the Weizmann Institute of Science prepared (Chem. Commun. 2015, 51, 9002. DOI: 10.1039/C5CC02902C) the alkene 17 by adding the phosphorane derived from 16 to the aldehyde derived from 15. In an extension of the Wenkert protocol, Magnus Rueping of RWTH Aachen University coupled (Chem. Commun. 2015, 51, 1937. DOI: 10.1039/C4CC08187K) the alkyl lithium 19 with the enol ether 18 to give the Z allyl silane 20. Amir H. Hoveyda of Boston College observed (Angew. Chem. Int. Ed. 2015, 54, 215. DOI: 10.1002/anie.201409120) high Z selectivity in the cross coupling metathesis of 21 with the vinyl borane 22 to give 23.

Jianbo Wang of Peking University showed (J. Org. Chem. 2015, 80, 647. DOI: 10.1021/jo502316q) that an α-diazo ester 24, readily prepared from the ester (J. Org. Chem. 2005, 70, 2851. DOI: 10.1021/jo048011o) could be condensed with acetylene to give the allene 25. Daniel Seidel of Rutgers University used (J. Am. Chem. Soc. 2015, 137, 4650. DOI: 10.1021/jacs.5b02071) a Cu catalyst to prepare the enantiomerically-enriched propargylic amine from the aldehyde 26 and the alkyne 27, and showed that addition of AgNO₃ converted that adduct to the allene 28 with maintenance of enantiomeric excess.

In the course of a synthesis of Tulearin A, Alois Fürstner of the Max-Planck-Institut für Kohlenforschung developed (Chem. Eur. J. 2015, 21, 219. DOI: 10.1002/chem.201404873) a procedure for converting a lactone 29 into the internal alkyne 30. Bo Liu of the Guangdong Provincial Academy of Chinese Medical Sciences and Biaolin Yin of the South China University of Technology fragmented (J. Org. Chem. 2015, 80, 2092. DOI: 10.1021/jo502328j) the furan 31 to the ene yne 32.

In an impressive display of (possibly equilibrating) alkyne metathesis, Alison N. Hulme of the University of Edinburgh cleanly dimerized (Angew. Chem. Int. Ed. 2015, 54, 7086. DOI: 10.1002/anie.201501922) the diyne 33 to the head to tail dimer 34. Deprotection followed by partial hydrogenation converted 34 into Disorazole C₁ (35).