Academic literature on the topic 'Urethane A/J'

Dasheng Leow of the National Tsing Hua University used (Eur. J. Org. Chem. 2014, 7347) photolysis to activate the air oxidation of hydrazine to generate diimide, that then reduced 1 selectively to 2. Kevin M. Peese of Bristol-Myers Squibb effected (Org. Lett. 2014, 16, 4444) ring-closing metathesis of 3 followed by in situ reduction to form 4. Jitendra K. Bera of the Indian Institute of Technology Kanpur effected (J. Am. Chem. Soc. 2014, 136, 13987) gentle oxidative cleavage of cyclooctene 5 to the dialde­hyde 6. Arumugam Sudalai of the National Chemical Laboratory observed (Org. Lett. 2014, 16, 5674) high regioselectivity in the oxidation of the alkene 7 to the ketone 8. Hao Xu of Georgia State University also observed (J. Am. Chem. Soc. 2014, 136, 13186) high regioselectivity in the oxidation of the alkene 9 with 10, leading to the urethane 11. Justin Du Bois of Stanford University developed (J. Am. Chem. Soc. 2014, 136, 13506) mild conditions for the net double amination of the alkene 12 with 13, leading to 14. Jiaxi Xu and Pingfan Li of the Beijing University of Chemical Technology devised (Org. Lett. 2014, 16, 6036) a protocol for the allylic thiomethylation of an alkene with 16, converting 15 to 17. Matthias Beller of the Leibniz-Institüt für Katalyse combined (Chem. Eur. J. 2014, 20, 15692) hydroformylation, aldol condensation, and reduction to convert the alkene 18 to the ketone 19. Phil S. Baran of Scripps/La Jolla added (Angew. Chem. Int. Ed. 2014, 53, 14382) the diazo dienone 21 to the alkene 20 to give, after exposure to HCl, the arylated product 22. Markus R. Heinrich of the Friedrich-Alexander-Universität Erlangen-Nürnberg employed (Chem. Eur. J. 2014, 20, 15344) Selectfluor as both an oxidizing and a fluorinating agent in the related addition of 24 to 23 to give 25. Debabrata Maiti at the Indian Institute of Technology Bombay activated (J. Am. Chem. Soc. 2014, 136, 13602) the ortho position of 27, then added that interme­diate to 26 to give 28.

Susumu Saito of Nagoya University developed (Angew. Chem. Int. Ed. 2011, 50, 3006) Fe-catalyzed conditions, compatible with alkenes, for converting an alcohol 1 to the amine 2. Corey R. J. Stephenson of Boston University took advantage (Nature Chem. 2011, 3, 140) of photoredox catalysis to convert an alcohol 3 to the iodide 4. Jing-Mei Huang of the South China University of Technology condensed (J. Org. Chem. 2011, 76, 3511) the halide 5 with benzaldehyde and aqueous ammonia to give the imine 6. Young Hoon Jung of Sungkyunkwan University used (Tetrahedron Lett. 2011, 52, 1901) chlorosulfonyl isocyanate to convert a benzylic (or allylic) ether 7 into the urethane 8. David Crich of Centre de Recherche de Gif coupled (Org. Lett. 2011, 13, 2256) the isocyanate 9 with the acid 10 to give the amide 11. Tobias Ritter of Harvard University effected (J. Am. Chem. Soc. 2011, 133, 1760) α-hydroxylation of the acidic ketone 12 by exposure to O2 in the presence of a Pd catalyst. Gowravaram Sabitha of the Indian Institute of Chemical Technology, Hyderabad, activated (Org. Lett. 2011, 13, 382) Pd(OH)2 by exposure to H2 , then used the activated catalyst to isomerize the allylic alcohol 14 to the aldehyde 15 . Richard C. Hartley of the University of Glasgow combined (Tetrahedron Lett. 2011, 52, 3020) commercial Nysted reagent and Cp2 TiCl2 to methyl-enate the ester 16. The enol ether 17 is a versatile intermediate, giving, inter alia, the methyl ketone by hydrolysis, or the α-hydroxy ketone on exposure to peracid. The activation of alkynes continues to be an area of vigorous investigation. Lukas Hintermann of the Technische Universitä t München devised (J. Am. Chem. Soc. 2011, 133, 8138) a Ru catalyst for the hydration of 18 to the aldehyde 19. Issa Yavari of Tarbiat Modares University effected (Tetrahedron Lett. 2011, 52, 668) oxidation of 20 to the N-sulfonyl amidine 22. Craig A. Merlic of UCLA coupled (Org. Lett. 2011, 13, 2778) 24 with the vinyl boronate derived from 23 to give the silyl enol ether 25. Li-Biao Han of AIST Tsukuba prepared (Chem. Commun. 2011, 47, 2333) 28 by adding 27 to 26.

Corey R. J. Stephenson of Boston University devised (Chem. Commun. 2011, 47, 5040) a protocol using visible light for removing the PMB group from 1 to give 2. John F. Hartwig, now at the University of California, Berkeley, developed (Science 2011, 332, 439) a Ni catalyst for the cleavage of the durable aryl ether of 3 to give 4. Mark S. Taylor of the University of Toronto devised (J. Am. Chem. Soc. 2011, 133, 3724) the catalyst 6, which selectively mediated esterifi cation of 5 to 7. Jean-Marie Beau of the Université Paris-Sud added (Chem. Commun. 2011, 47, 2146) Et3 SiH following the Fe-catalyzed deprotection-protection of 8, resulting in clean conversion to the bis ether 9. Mahmood Tajbakhsh of the University of Mazandaran showed (Tetrahedron Lett. 2011, 52, 1260) that guanidine HCl catalyzed the conversion of 10 to 11. Stephen W. Wright of Pfizer/Groton established (Tetrahedron Lett. 2011, 52, 3171) that the new urethane protecting group of 12, stable to many conditions, could be deprotected to 13 under conditions that spared even a Boc group. Matthias Beller of the Leibniz-Institute for Catalysis protected (Chem. Commun. 2011, 47, 2152) the amine 14 as the readily hydrolyzed imidazole 16. Sentaro Okamoto of Kanagawa University found (Org. Lett. 2011, 13, 2626) a simple reagent combination for the removal of the sometimes reluctant sulfonamide from 17. Jordi Burés and Jaume Vilarrasa of the Universitat de Barcelona removed (Angew. Chem. Int. Ed. 2011, 50, 3275) the oxime from 19 by Au-catalyzed exchange with 20. Pengfei Wang of the University of Alabama, Birmingham, designed (J. Org. Chem. 2011, 76, 2040) a range of photochemically removable protecting groups for aldehydes and ketones. Rafael Robles of the University of Granada selectively protected (J. Org. Chem. 2011, 76, 2277) the diol 24 using the reagent created by the activation of 25. Berit Olofsson of Stockholm University prepared (Org. Lett. 2011, 13, 3462) the phenyl ester 28 by exposing 27 to the diaryl iodonium triflate. Kannoth Manheri Muraleedharan of the Indian Institute of Technology, Madras, selectively (Org. Lett. 2011, 13, 1932) esterified 29 to 30 with catalytic SmCl3.

Vlada B. Urlacher of the Heinrich-Heine University Düsseldorf showed (Chem. Commun. 2014, 50, 4089) that the P450 monooxygenase CYP154A8 from Nocardia farcinica could monohydroxylate n-octane 1 to 2 with high regioselectivity and ee. Fener Chen of Fudan University used (J. Org. Chem. 2014, 79, 2723) an organocatalyst to open the prochiral anhydride 3 to the monoester 4. Amir H. Hoveyda of Boston College added (Angew. Chem. Int. Ed. 2014, 53, 3387) (pinacolato)borane to the enone 5 to give 6, that was readily oxidized to the tertiary alcohol. Matthias Breuning of the University of Bayreuth designed (Chem. Commun. 2014, 50, 6623) a Cu catalyst for the enantioselective Henry addition of nitromethane to the aldehyde 7 to give 8. Benjamin List of the Max-Planck-Institute für Kohlenforschung optimized (Synlett 2014, 25, 932) the proline-catalyzed formation of the aldol prod­uct 10 from the aldehyde 9. Christian Wolf of Georgetown University devised (Chem. Commun. 2014, 50, 3151) the alkyne 12, that could be added to the aldehyde 11 to give 13 in high ee. Keiji Maruoka of Kyoto University developed (Org. Lett. 2014, 16, 1530) practical conditions for the organocatalyzed addition of an aldehyde 14 to an in situ- generated nitroso urethane, leading, after reduction, to the alcohol 15. Satoko Kezuka of Tokai University added (Tetrahedron Lett. 2014, 55, 2818) the benzyloxyamine 17 to the nitro alkene 16 to give the coupled product 18 in high ee. Xiaohua Liu and Xiaoming Feng of Sichuan University developed (Angew. Chem. Int. Ed. 2014, 53, 1636) a Pd catalyst for the preparation of 20 by the enantioselective amination of the diazo ester 19. Shou-Fei Zhu and Qi-Lin Zhou of Nankai University described (Angew. Chem. Int. Ed. 2014, 53, 2978) related work, not illustrated, on the enantioselective aryloxylation of an α-diazo ester. Alan Armstrong of Imperial College London, taking advantage (J. Org. Chem. 2014, 79, 3895) of the ready availability of enantiomerically secondary selenides such as 21, showed that it could be combined with 22 to give the α-chiral amine 23.

Welwitindolinone A Isonitrile 3 is the first of a family of oxindole natural products isolated from the cyanobacteria Hapalosiphon welwischii and Westiella intricate on the basis of their activity for reversing multiple drug resistance (MDR). A key transformation in the total synthesis of 3 reported (J. Am. Chem. Soc. 2008, 130, 2087) by John L. Wood, now at Colorado State University, was the chlorination of 1, that in one step established both the axial secondary chloro substituent and the flanking chiral quaternary center. The starting material for the synthesis of 3 was the diene acetonide 5, readily prepared from the Birch reduction product 4. Intermolecular ketene cycloaddition proceeded with high regio- and diastereoselectivity, to give the bicyclooctenone 6. The triazene-bearing Grignard reagent 7 added to the ketone 6 with the anticipated high diastereocontrol, to give, after reduction and protection, the cyclic urethane 8. Selective oxidation of the diol derived from 8 followed by silylation delivered the enone 9. Conjugate addition of hydride followed by enolate trapping gave the trifl ate 10. Pd-catalyzed meth-oxycarbonylation established the methyl ester 11. Addition of CH3MgBr to 11 gave 1, setting the stage for the establishment of the two key stereogenic centers of 2 and so of 3. The transformation of 1 to 2 was envisioned as being initiated by formation of a bridging chloronium ion. Pinacol-like 1,2-methyl migration then proceeded to form the trans diaxial product, moving the ketone-bearing branch equatorial. In addition to being an elegant solution of the problem of how to establish the axial chloro substituent of 3, this strategy might have some generality for the stereocontrolled construction of other alkylated cyclic quaternary centers. Reduction of the ketone 2 and dehydration of the resulting alcohol led, after deprotection and oxidation, to the ketone 12. Protection followed by β-elimination gave the enone 13. Direct reductive amination of 13 failed, but reduction of the methoxime was successful, giving, after acylation, the formamide 14. Reductive N-O bond cleavage followed by deprotection and isonitrile formation then set the stage for the planned intramolecular acylation to complete the synthesis of Welwitindolinone A Isonitrile 3.