  We describe quasi-Hopf twist deformations of flat closed string
compactifications with non-geometric R-flux using a suitable cochain twist, and
construct nonassociative deformations of fields and differential calculus. We
report on our new findings in using this formalism to construct perturbative
nonassociative field theories on these backgrounds. We describe the
modifications to the usual classification of Feynman diagrams into planar and
non-planar graphs. The example of phi(4) theory is studied in detail and the
one-loop contributions to the two-point function are calculated.
