The stereochemistry of some 7-hydroxyindene dimers: applications of ¹H nuclear magnetic resonance relaxation pathway analysis

Abstract

1H spin-lattice relaxation rates and nuclear Overhauser effect difference spectra have been measured (at 400 MHz) for six dimers derived from methyl-substituted 7-hydroxyindenes. Used in combination, these measurements identify the relaxation pathways available to all of the protons in the molecules. Analysis of these pathways has permitted assignment of all chemical shifts, and identification of the relative stereochemistry at all chiral centres.

The dimerisation of some 4-hydroxyindenes

“…dilute methanolic sulphuric acid. Similar treatment of the 1 -butylindanols gave acceptable yields of butylindenes (3) and (4) but the product mixture from (3) contained up to 20% of the alkene (11), characterised as the exocyclic isomer by a 4 J H H coupling of 7 Hz between the C-2 methylene protons and the C-1' vinyl proton, much greater than that observed (1)(2) in the endocyclic indenes. The (E)-stereochemistry is assumed for (11) as this stereoisomer should be the more stable.…”

“…102.5-103.5 "C (from pentane) (lit.,' 101.5-102 "C); 6, (CDCl, + 2% Et3N) 16. , 127.2 (C-2), 13 1.6 (C-7), 139.9 (C-3), 145.7 (C-7a), and 148.8 (C-4). 2,3',4,.-Sulphuric acid (2 moll-'; 10 ml) was added to the alcohol (8) (0.55 g) in methanol (40 ml) at room temperature. After 90 min, water (200 ml) was added and work-up gave the crude product (0.48 g).…”

“…relaxation pathway analysis. 2 In this paper we report on the synthesis and interconversion of these dimers and their congeners, and on the application of ' 3C n.m.r. spectroscopy to the structural elucidation of these compounds.…”