Ring-chain tautomerism and crystal structure of some 1,3-oxazacyclanes, and the electrophilic substituent constants for some heteroaryl groups in solution and in the gas-phase

Ferenc Fülöp, Reijo Sillanpää, Martti Dahlqvist, Kalevi Pihlaja, Pirjo Vainiotalo

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19 Citations (Scopus)

Abstract

In principle, the ring-chain tautomeric ratios of a number of 2-heteroaryl-substituted oxazolidines and tetrahydro-1,3-oxazines are well suited for determination of the Hammett-Brown σ+ constants of heteroaryl substituents such as 2-furyl, 3-furyl, 3-thienyl and 2-pyrrolyl in CDCl3 solution and in the gas phase. However, a number of factors, and especially hydrogenbonding, can change the monomeric character of either the ring or the chain form (or both), leading to deviations from the ideal σ+ values. X-Ray analysis has demonstrated the chain structures of the products of the reactions of l-(-)-norpseudoephedrine and (±)-trans-2-aminomethylcyclo-hexanol with pyrrole-2-carboxaldehyde.

Original languageEnglish
Pages (from-to)1093-1107
Number of pages15
JournalHeterocycles
Volume37
Issue number2
Publication statusPublished - Mar 3 1994

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ASJC Scopus subject areas

  • Analytical Chemistry
  • Pharmacology
  • Organic Chemistry

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