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Full-Text Articles in Physical Sciences and Mathematics

Dehydrotropylium-Co2(Co)6 Ion. Generation, Reactivity And Evaluation Of Cation Stability, Sheida Amiralaei, James Gauld, James R. Green Apr 2011

Dehydrotropylium-Co2(Co)6 Ion. Generation, Reactivity And Evaluation Of Cation Stability, Sheida Amiralaei, James Gauld, James R. Green

Chemistry and Biochemistry Publications

The dehydrotropylium–Co2(CO)6 ion was generated by the action of HBF4 or BF3OEt2 on the corresponding cycloheptadienynol complex, which in turn has been prepared in four steps from a known diacetoxycycloheptenyne complex. The reaction of the cycloheptadienynol complex via the dehydrotropylium–Co2(CO)6 ion with several nucleophiles results in substitution reactions with reactive nucleophiles (N>1) under normal conditions, and a radical dimerisation reaction in the presence of less reactive nucleophiles. Competitive reactions of the cycloheptadienynol complex with an acyclic trienynol complex show no preference for generation of the dehydrotropylium–Co2 …


Synthesis Of ‘Spacer’-Naproxen [2-(6-Methoxybiphenylen-2-Yl)Propanoic Acid] And -Isonaproxen [2-(7-Methoxybiphenylen-2-Yl)Propanoic Acid], Juan A. González Gómez, James R. Green, Peter C. Vollhardt Apr 2011

Synthesis Of ‘Spacer’-Naproxen [2-(6-Methoxybiphenylen-2-Yl)Propanoic Acid] And -Isonaproxen [2-(7-Methoxybiphenylen-2-Yl)Propanoic Acid], Juan A. González Gómez, James R. Green, Peter C. Vollhardt

Chemistry and Biochemistry Publications

The CpCo(CO)2-catalyzed cocyclization of 1,2-diethynyl- 4-methoxybenzene with alkynes can be applied to the synthesis of ‘spacer’-naproxen [2-(6-methoxybiphenylen-2-yl)propanoic acid] and its 7-methoxy isomer, ‘spacer’-isonaproxen. While unsymmetrical alkynes are incorporated without regioselectivity, the methoxy group in 6-methoxy-2,3-bis(trimethylsilyl)biphenylene directs electrophiles to C-3, thus allowing for regiochemical differentiation between the 2- and 3-positions.


Nicholas Reactions In The Construction Of Cyclohepta[De]Naphthalenes And Cyclohepta[De]Naphthalenones. The Total Synthesis Of Microstegiol, Rafiq Taj, James R. Green Dec 2010

Nicholas Reactions In The Construction Of Cyclohepta[De]Naphthalenes And Cyclohepta[De]Naphthalenones. The Total Synthesis Of Microstegiol, Rafiq Taj, James R. Green

Chemistry and Biochemistry Publications

The application of the Nicholas reaction chemistry of 2,7-dioxygenated naphthalenes in the synthesis of cyclohepta[de]napthalenes and in the synthesis of (±)-microstegiol (1) is presented. The substitution profile of Nicholas monosubstitution (predominantly C-1) and disubstitution reactions (predominantly 1,6-) on 2,7-dioxygenated napthalenes is reported. Application of a 1,8-dicondensation product and selected C-1 monocondensation products to the construction of cyclohepta[de]naphthalenes by way of ring closing metathesis and intramolecular Friedel−Crafts reactions, respectively, is described. Deprotection of the C-7 oxygen function to the corresponding naphthol allows tautomerization to cyclohepta[de]naphthalene-1-ones upon seven-membered-ring closure in most cases, and replacement …


Intramolecular Nicholas Reactions In The Synthesis Of Dibenzocycloheptanes. Synthesis Of Allocolchicine Nsc 51046 And Analogues And The Formal Synthesis Of (−)-Allocolchicine, Sinisa Djurdjevic, Fei Yang, James R. Green Dec 2010

Intramolecular Nicholas Reactions In The Synthesis Of Dibenzocycloheptanes. Synthesis Of Allocolchicine Nsc 51046 And Analogues And The Formal Synthesis Of (−)-Allocolchicine, Sinisa Djurdjevic, Fei Yang, James R. Green

Chemistry and Biochemistry Publications

The preparation of dibenzocycloheptyne-Co2(CO)6 complexes by intramolecular Nicholas reactions of biaryl-2-propargyl alcohol-Co2(CO)6 derivatives is described. Reductive decomplexation of the dibenzocycloheptyne-Co2(CO)6 complexes affords the corresponding dibenzocycloheptenes, individual members of which have been employed in a formal total synthesis of (−)-allocolchicine, the preparation of 6,7-dihydro-3,4,9,10,11-pentamethoxy-5H-dibenzo[a,c]cyclohepten-5-one, and the enantioselective total syntheses of NSC 51046 and its 3,8,9,10-tetramethoxy regioisomer.