Infrared absorption spectra were recorded on a Perkin-Elmer 1710 Fourier-transform or a 1600 series FTIR spectrophotometer. The spectra were recorded as thin films.
Proton nmr spectra were recorded on a Perkin-Elmer R-32 (90 MHz) referenced to tetramethylsilane or on a Bruker AC-300 (300 MHz) or AC-250 (250MHz) referenced to the deuterochloroform lock. Samples were run in deuterochloroform. The chemical shifts are quoted in delta and followed by the integration value, the signal multiplicity, coupling constants (J) and proton assignment. The following abbreviations have been used to describe signal multiplicity:-
br = broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet. Where necessary assignments have been confirmed by spin-spin decoupling. 13-C Nmr spectra were recorded on a Bruker AC-300 (75.47 MHz) or AC-250 (62.9 MHz) referenced to the deuterochloroform lock. The chemical shifts are quoted in delta followed by the assignment where known. Where necessary assignments have been confirmed on the basis of DEPT 135.138 spectra.
Low resolution mass spectra (E.I. and C.I.) were recorded on a Finnigan 4500 at Salford. FAB mass spectra and high resolution mass spectra (E.I., C.I. and FAB) were measured on a Kratos concept at Manchester. Capillary gas-chromatography was carried out on a Perkin-Elmer 8320 instrument using an "SGE" vitreous silica column (25QC2/BP1 0.25) and flame ionisation detection. G.C.M.S. was carried out on a Varian 3400 using a similar column and M.S. detection was carried out using the same Finnigan 4500.
Melting points were determined using an "Electrothermal" apparatus and are uncorrected or corrected against an appropriate standard. Elemental analysis was carried out by Butterworth Laboratories Ltd. or by C.H.N. Analysis Ltd. Optical rotations were measured using an AA-10 monochromatic 589 nm polarimeter (Optical Activity Ltd.). Concentrations are expressed in grams per 100 ml of solvent.
Thin layer chromatography was performed using Merck aluminium sheets, silica gel 60 F254, layer thickness 0.2 mm (Art. 5554). The plates were visualised by use of ultraviolet light and ethanolic vanillin or aqueous potassium permanganate. Silica gel (particle sizes 0.040-0.063 mm) supplied by E.M. Merck was employed for flash chromatography.
Diethyl ether ("ether") and tetrahydrofuran (THF) were distilled from sodium/benzophenone ketyl immediately prior to use. Dichloromethane was distilled from calcium hydride prior to use. Dimethylsulphoxide, triethylamine and diisopropylamine were distilled from calcium hydride and stored over 3Å molecular sieves. "Petrol" refers to 40-60 petroleum ether.
Reactions were routinely carried out under an argon or nitrogen atmosphere. Products were dried over anhydrous magnesium sulphate or anhydrous sodium sulphate as specified. After filtering, the mixtures were concentrated in vacuo at ~15 mmHg and at ~0.1 mmHg where appropriate to remove residual traces of solvent. Butyllithium ( = nbutyllithium, ~ 1.5M in hexanes) was supplied by Lithco Corporation and was standardised by titration using diphenylacetic acid as indicator. Several sources of methyllithium were employed. The most consistent results were obtained with that supplied by Janssen Chimica, (~ 1.4M in ether), standardised by titration using diphenylacetic acid as indicator. Chromium(II) chloride was kindly donated by British Bio-technology Ltd. originating from Johnson-Matthey, Materials Technology U.K.
Compounds have been named according to the substitutive nomenclature as described by Fresenius.
Compound Numbering (as used in nmr assignments)