  Context: The R CrA cloud hosts a handful of Class 0/I low-mass young stellar
objects. The chemistry and physics at scales $>500$ AU in this cloud are
dominated by the irradiation from the nearby Herbig Be star R CrA. The luminous
large-scale emission makes it necessary to use high-resolution spectral imaging
to study the chemistry and dynamics of the inner envelopes and discs of the
protostars.
  Aims: We aim to better understand the structure of the inner regions of these
protostars and, in particular, the interplay between the chemistry and the
presence of discs.
  Methods: Using Atacama Large Millimeter/submillimeter Array (ALMA)
high-resolution spectral imaging interferometry observations, we study the
molecular line and dust continuum emission at submillimetre wavelengths.
  Results: We detect dust continuum emission from four circumstellar discs
around Class 0/I objects within the R CrA cloud. Towards IRS7B we detect
C$^{17}$O emission showing a rotation curve consistent with a Keplerian disc
with a well-defined edge that gives a good estimate for the disc radius at 50
AU. We derive the central object mass to $2.3M_{\odot}$ and the disc mass to
$0.024M_{\odot}$. The observations are also consistent with a model of material
infalling under conservation of angular momentum; however, this model provides
a worse fit to the data. We also report a likely detection of faint CH$_3$OH
emission towards this point source, as well as more luminous CH$_3$OH emission
in an outflow orthogonal to the major axis of the C$^{17}$O emission.
  Conclusions: The faint CH$_3$OH emission seen towards IRS7B can be explained
by a flat density profile of the inner envelope caused by the disc with a
radius $\lesssim50$ AU. We propose that the regions of the envelopes where
complex organic molecules are present in Class 0/I young stellar objects can
become quenched as the disc grows.
