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In all three title compounds, C7H12O4, (1), C9H12O4, (2), and C7H12O2S2, (3), the spiro C-O distances are substantially shorter than the non-spiro C-O distances as a result of the anomeric effect. In contrast, the spiro C-S distances of compound (3) are similar to the non-spiro C-S distances. In all three compounds, steric repulsions between the lone pairs on the O or S atoms and the axial H atoms of the opposite ring result in a distorted geometry around the spiro-C atoms.
Supporting information
![cif](https://journals.iucr.org//../logos/filetypeicons/bw/b1/ciflogo.png) | Crystallographic Information File (CIF) Contains datablocks s476, s477, dhs_3, global |
![fcf](https://journals.iucr.org//../logos/filetypeicons/bw/b1/fcflogo.png) | Structure factor file (CIF format) Contains datablock s476 |
![fcf](https://journals.iucr.org//../logos/filetypeicons/bw/b1/fcflogo.png) | Structure factor file (CIF format) Contains datablock s477 |
![fcf](https://journals.iucr.org//../logos/filetypeicons/bw/b1/fcflogo.png) | Structure factor file (CIF format) Contains datablock dhs_3 |
CCDC references: 130212; 130213; 130214
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