Stereoselective cyclotetramerization of a 3-(Hydroxymethyl)salicylaldehyde
Both 3-(hydroxymethyl)-5-methylsalicylaldehyde and its acetonide condense in the presence of hydrogen chloride in ether to form macrocyclic S(4)-symmetric tetraacetal 2. The reaction is completely oligo- and stereoselective, forming only the tetramer and only the achiral (R,S,R,S)-stereoisomer. Acid-catalyzed equilibration studies and molecular mechanics calculations indicate that the stereoselectivity is thermodynamic in origin. In the crystal the saddle-shaped molecules of 2 form coaxial stacks reminiscent of the packing of Pringles potato chips.
Butler
GM
Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556-5670, USA.
Brown
SN
Boger
RM
Ferfolia
MT
Fitzgibbons
AC
Jongeling
AC
Kelleher
SJ
Malec
AD
Malerich
J
Weltner
AN