We report the dynamic self-assembly of chemically propelled nanoscale building blocks (NBBs) under confinement using reactive molecular dynamics simulations. The NBBs are hollow rectangles with one side open (tail) to expose the catalysts inside to the fuel environment. Adjacent NBBs can self assembly into tail-tail or tail-head (the side opposite to the tail) pairs. It was found that chemical propulsion forces unlock many tail-tail pairs but not tail-head pairs. Although the distributions of both tail-tail and tail-head pairs are orientation-dependent with respect to the confining wall, the effect of chemistry seems to be orientation-independent. (C) 2012 Elsevier B.V. All rights reserved.