New 1, 3-dithiol-2-ylidene derivatives, notably π-extended systems, have been synthesised by Wittig reactions of phosphorane and phosphonate ester derivatives of 1, 3-dithiole with activated ketones and α, β-unsaturated ketones. Nitrosation reactions of a range of these π- extended systems, results in the formation of nitroalkenes, via unstable nitrosoalkene intermediates, which, in general, could not be isolated. The X-ray crystal structure of 1-(4, ...