In Ti(IV)-promoted reactions with 2-methoxy-1,4-benzoquinones 3, thioallenes 1 give 2 + 2 and/or 3 + 2 products via attack on a C = C moiety of the quinone, whereas silylallene 2 gives products derived from attack on a carbonyl group of the quinone.
Engler, T. A., Agrios, K., Reddy, J. P., & Iyengar, R. (1996). Contrasting reactivity in Lewis acid-promoted reactions of thio- and silyl-allenes with 1,4-benzoquinones. Tetrahedron Letters, 37(3), 327–330. https://doi.org/10.1016/0040-4039(95)02164-7