The acetaldehyde compounds, 2-thiobenzoylacetaldehyde diethylacetal, 2-benzoyloxyacetaldehyde bis(2-methoxyethyl)acetal, 2-hydroxyacetaldehyde bis( 2-methoxyethyl)acetal, 2-thiobenzoylacetaldehyde bis(2-methoxy-ethyl)acetal, and 2-thioacetaldehyde bis(2-methoxyethyl)acetal, are useful as intermediates in the synthesis of substituted 1,3-oxathiolanes and substituted 1,3-dioxolanes.