Solfege Syllables of Secondary Dominants and Secondary Leading tone chords in Major

Secondary Dominant Triads Double the root in 4 parts Notice that the V/IV is undistinguishable from a I chord
Re	Mi	Fi	Sol	La	Ti
Ti	Di	Ri	Mi	Fi	Si
Sol	La	Ti	Do	Re	Mi
V	V/ii	V/iii	V/IV	V/V	V/vi

Secondary Dominant Sevenths
Fa	Sol	La	Ti	Do	Re
Re	Mi	Fi	Sol	La	Ti
Ti	Di	Ri	Mi	Fi	Si
Sol	La	Ti	Do	Re	Mi
V⁷	V⁷/ii	V⁷/iii	V⁷/IV	V⁷/V	V⁷/vi

Secondary Leading-tone Triads In 4 parts it is customary to Double the third of a diminished chord
Fa	Sol	La	Ti	Do	Re
Re	Mi	Fi	Sol	La	Ti
Ti	Di	Ri	Mi	Fi	Si
vii^°	vii^°/ii	vii^°/iii	vii^°/IV	vii^°/V	vii^°/vi

Secondary Leading-tone Sevenths
La	Te	Do	Re	Mi	Fa
Fa	Sol	La	Ti	Do	Re
Re	Mi	Fi	Sol	La	Ti
Ti	Di	Ri	Mi	Fi	Si
vii Ø⁷	vii^°⁷/ii	vii^°⁷/iii	vii Ø⁷/IV	vii Ø⁷/V	vii^°⁷/vi