I consider a theoretical description of recent experiments on doping the sp
in-Peierls compound CuGeO3 and the Haldane gap compounds PbNi2V2O8 and Y2Ba
NiO5. The effective theory is the one of randomly distributed spin-1/2 mome
nts interacting with an exchange decaying exponentially with distance. The
model has: two phases in the (doping, interchain coupling) plane: (i) a Nee
l ordered phase at small doping; (ii) a quantum disordered phase at larger
doping and small interchain interactions. The spin-Peierls compound CuGeO3
and the Haldane gap nickel oxides PbNi2V2O8 and Y2BaNiO5 fit well into this
phase diagram. At small temperature, the Neel phase is found to be reentra
nt into the quantum disordered region. The Neel transition relevant for CuG
eO3 and PbNi2V2O8 can be described in terms of a classical disordered model
. A simplified version of this model is introduced, and is solved on a hier
archical lattice structure, which allows to discuss the renormalization gro
up flow of the model. It is found that the system looks non disordered at l
arge scale, which is not against available susceptibility experiments. In t
he quantum disordered regime relevant for Y2BaNiO5, the two spin model and
the cluster RG in the 1D regime show a power law susceptibility, in agreeme
nt with recent experiments on Y2BaNiO5. It is found that there is a success
ion of two distinct quantum disordered phases as the temperature is decreas
ed. The classical disordered model of the doped spin-1 chain contains alrea
dy a physics relevant to the quantum disordered phase.