${}^{12}\mathrm{C}(\stackrel{\ensuremath{\rightarrow}}{p},d{\ensuremath{\pi}}^{+}{)}^{11}\mathrm{B}$ has been investigated in the quasifree region at energies of 370 and 500 MeV. For each energy, measurements were made at the four angle combinations of $({\ensuremath{\theta}}_{d,\mathrm{left}},{\ensuremath{\theta}}_{\ensuremath{\pi},\mathrm{right}})$ equal to (15\ifmmode^\circ\else\textdegree\fi{}, 30\ifmmode^\circ\else\textdegree\fi{}), (15\ifmmode^\circ\else\textdegree\fi{}, 55\ifmmode^\circ\else\textdegree\fi{}), (25\ifmmode^\circ\else\textdegree\fi{}, 30\ifmmode^\circ\else\textdegree\fi{}), and (25\ifmmode^\circ\else\textdegree\fi{}, 55\ifmmode^\circ\else\textdegree\fi{}). In addition to strong excitation of the g.s. ${3/2}^{\ensuremath{-}}$ state, the 2.12 MeV ${1/2}^{\ensuremath{-}}$ and 5.02 MeV ${3/2}^{\ensuremath{-}}$ states are also excited with appreciable strength. Furthermore, a broad continuum at an excitation energy of about 20 MeV, corresponding to the ${1s}_{1/2}$ hole state is prominently seen. The pion differential cross section distributions exhibit maxima when the recoil nucleus momenta are at a minimum. Analyzing powers were obtained over the range of pion energies investigated. Several measurements for the ${}^{2}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{p},d{\ensuremath{\pi}}^{+})n$ reaction are also reported. The results are compared with plane-wave impulse approximation and distorted-wave impulse approximation calculations.