The crystal structures and Hirshfeld surface analysis of 6-(naphthalen-1-yl)-6a-nitro-6,6a,6b,7,9,11a-hexa-hydro-spiro-[chromeno[3',4':3,4]pyrrolo-[1,2-c]thia-zole-11,11'-indeno-[1,2-b]quinoxaline] and 6'-(naphthalen-1-yl)-6a'-nitro-6',6a',6b',7',8',9',10',12a'-octa-hydro-2H-spiro-[ace-naphthyl-ene-1,12'-chromeno[3,4-a]indolizin]-2-one.

The title compounds, 6-(naphthalen-1-yl)-6a-nitro-6,6a,6†b,7,9,11a-hexa-hydro-spiro-[chromeno[3',4':3,4]pyrrolo-[1,2-c]thia-zole-11,11'-indeno-[1,2-b]quinoxaline], C(37)H(26)N(4)O(3)S, (I), and 6'-(naphthalen-1-yl)-6a'-nitro-6',6a',6b',7',8',9',10',12a'-octa-hydro-2H-spiro-[ace-naphthyl-ene-1,12'-chromeno[3,4-a]indolizin]-2-one, C(36)H(28)N(2)O(4), (II), are new spiro derivatives, in which both the pyrrolidine rings adopt twisted conformations. In (I), the five-membered thia-zole ring adopts an envelope conformation, while the eight-membered pyrrolidine-thia-zole ring adopts a boat conformation. An intra-molecular C-H⋯N hydrogen bond occurs, involving a C atom of the pyran ring and an N atom of the pyrazine ring. In (II), the six-membered piperidine ring adopts a chair conformation. An intra-molecular C-H⋯O hydrogen bond occurs, involving a C atom of the pyrrolidine ring and the keto O atom. For both compounds, the crystal structure is stabilized by inter-molecular C-H⋯O hydrogen bonds. In (I), the C-H⋯O hydrogen bonds link adjacent mol-ecules, forming R (2) (2)(16) loops propagating along the b-axis direction, while in (II) they form zigzag chains along the b-axis direction. In both compounds, C-H⋯π inter-actions help to consolidate the structure, but no significant π-π inter-actions with centroid-centroid distances of less than 4†à are observed.