The interval J = (−1, 1) turns into a Lie group under the group operation x • y := (x + y)(1 + xy) −1 ,x, y ∈ J . This enables definition of the invariant measure dJ (x) := (1 − x 2 ) −1 dx and the Fourier transform F J on the interval J and, as a consequence, we can consider Fourier convolution operators W 0 J ,a := F J −1 aF J on J . This class of convolutions includes celebrated Prandtl, Tricomi and Lavrentjev-Bitsadze equations and, also, differential equations of arbitrary order with the natural weighted derivative D J u(x) = −(1 − x 2 )u ′ (x), t ∈ J . Equations are solved in the scale of Bessel potential H s p (J , dJ (x)), 1 p ∞, and Hölder-Zygmound Z ν (J ), 0 < µ, ν < ∞ spaces, adapted to the group J . Boundedness of convolution operators (the problem of multipliers) is discussed. The symbol a(ξ), ξ ∈ R, of a convolution equation W 0 J ,a u = f defines solvability: the equation is uniquely solvable if and only if the symbol a is elliptic. The solution is written explicitly with the help of the inverse symbol.We touch shortly the multidimensional analogue-the Lie group J n .