Satomi Niwayama

Competition between ester and formyl groups for control of torquoselectivity in cyclobutene electrocyclic reactions

Abstract Methyl 3-formylcyclobutene-3-carboxylate was synthesized in five steps from commercially available cyclobutane-1,1-dicarboxylic acid. Thermolysis afforded methyl (2H)-pyrane-5-carboxylate, which was formed by electrocyclization of the formyl-in, ester-out product of ring opening. This confirms theoretical predictions.

Lewis acid reversal of the torquoselectivity of the electrocyclic ring opening of 3-acetylcyclobutene

Abstract Thermolysis of 3-acetylcyclobutene resulted in a mixture of E-and Z-dienes, favoring slightly the E-diene, in accord with theoretical prediction. This preference was reversed by the Lewis acid, ZnI 2 , also predicted by ab initio calculations on a model system.

Remote Exo/Endo Selectivity in Selective Monohydrolysis of Dialkyl Bicyclo[2.2.1]heptane-2,3-dicarboxylate Derivatives

High exo-facial selectivity was observed in the selective monohydrolysis of a series of near-symmetric diesters that possess an exo-ester group and an endo-ester group attached on a norbornane or norbornene skeleton. The selectivities were found to be clear-cut, although the reaction center in these reactions is one covalent bond distant from the norbornane or norbornene ring, where the difference of the environment between the exo face and endo face is therefore expected to be negligible. The effect of the co-solvent we studied earlier for the selective monohydrolysis reaction was also confirmed and contributed to improvement of the yields of the half-esters.

THE TORQUOSELECTIVITY OF ELECTROCYCLIC REACTIONS OF 3-DONOR-3-ACCEPTOR-SUBSTITUTED CYCLOBUTENES

Abstract Theory predicts that electron donors have larger outward rotation preferences than acceptors in thermal ring openings of cyclobutenes. Experimental verifications are presented for several 3,3-disubstituted cyclobutenes.

Competition between carbomethoxy and carboxyl in electrocyclic opening of a 3,3-disubstituted cyclobutene

Abstract Thermolysis of 3-carbomethoxycyclobutene-3-carboxylic acid afforded two dienes in equal amounts, which is consistent with our prediction. The structures of the dienes were determined by long range coupling constants between the carbonyls and β-olefinic protons by long range selective proton decoupling. theoretical prediction. The structure analysis of the dienes was made by 3JCH long range coupling constants between the carbonyls and the β-protons.