Helical arrangements and the associated chirality have wellknown implications in a variety of areas ranging from natural biological systems to materials science. In particular orthofused polyaromatic systems with p-conjugated helical structures display unique physicochemical properties which have stimulated countless studies [1] oriented towards self-assembly and chiral recognition, [2] chiroptical devices, [3] molecular machines, [4] material chemistry, [5] organometallic and organocatalysis, [6, 7] as well as asymmetric synthesis. [8, 9] In the general context of the growing interest in helical derivatives, helicenes displaying phosphorus functions represent promising scaffolds. Trivalent phosphorus functions and the related metal complexes are easily designed to tune the electronic and physicochemical properties of helicenes, [10] as well as to offer a wide range of potential uses in organometallic chemistry and catalysis. It is therefore rather surprising to note that the field today is still in its infancy, first of all in terms of number of compounds as well as structural diversity. So far, most phosphorus derivatives having helical chirality display polyaromatic (or heteroaromatic) helical scaffolds with pendant phosphorus functions (phosphites, [2a, 6b, 11] trivalent phosphines and phosphine oxides, [6a, 12] phospholes, [10a,b] etc.). Very little is known about their properties and behaviors.The aim of this work is to expand the range of heterohelicenes to chiral helicenes where phosphorus is embedded within the helical framework itself, at the external edge of the fused ring sequence (Figure 1). Helical phosphines of this class would not only display peculiar electronic features resulting from extended p conjugation, but also take full advantage of the dissymmetric steric environment generated by the helical chirality at the external edge. Helicenes of this class are unknown to date, whereas phosphahelicenes, wherein phosphorus is embedded in the internal section of the helical framework, have been reported only recently by Tanaka and co-workers and Nozaki and co-workers. [13] We intend to disclose here: a) the first diastereo-and enantioselective access to [6]-and [7]helicenes in which the fused ring sequence ends with a phosphole unit; b) the structural and chiroptical properties of enantiomerically pure derivatives of this class; c) the enantiospecific self-assembly of columnar arrangements in the solid state; and d) the photochemical [2+2] annulations of phosphole-fused [6]helicenes into dimeric helical structures.When targeting helicenes where phosphorus is embedded within the helical framework itself, we envisioned 1Hphosphindole oxides as suitable building blocks and have adapted the classical helicene synthesis, based on the photochemical cyclization/dehydrogenation of diarylolefins, to these substrates. [14] Our starting materials are the olefins 5 which combine a 1H-phosphindole unit and a benzo[c]phenanthrene fragment. They have been prepared according to a known procedure, [15] by usi...
