If is a finite Coxeter group then the associated Solomon’s descent algebra is certain subalgebra of the integral group algebra discovered/introduced in
L. Solomon, A Mackey formula in the group ring of a Coxeter group, J. Algebra 41, (1976), 255-268, MR0444756, doi
Other literature
Mike Atkinson, A new proof of a theorem of Solomon, Bull. London Math. Soc. 18 (1986), 351-354; Solomon’s descent algebra revisited, Bull. London Math. Soc. 24 (1992), 545-551.
Goetz Pfeiffer, A quiver presentation for Solomon’s descent algebra, arxiv/0709.3914