The bonding character between the bridgehead carbon atoms inferred from the longer C-C distance in the triplet state as opposed to the singlet9 is consistent with our conclusion that this pair contributes significantly to the bonding.

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152ChemInform Abstract The aldehydes (II) are smoothly converted to the haloolefins (III), (IV), (V) using the title system (i.e. the haloforms (I) and conditions (A) or (B)). The (E)-isomers are formed with high selectivity in all cases except (IIIe) (the numbers in parentheses denote the E/Z ratios). Condition (B) is used in the case of (Ib) (→ (IV)) in order to avoid the additional formation of chloro compounds (V) as it occurs in the reactions of (IIa), (IIb) with (Ib) under the condition (A). Ketones are less reactive than aldehydes. The selective onversion in the presence of a ketone into E-iodo olefin is demonstrated using the substrates (IIa) + (VI). The monoiodide (VIII) is mainly formed from the ketoaldehyde (VII). Furthermore, addition of aldehydes to the alkenyl halide formed provides a simple route to E)-allylic alcohols such as (X).

ChemInform Abstract Reductive coupling of the acetals (I) with the aldehydes (II) in the presence of chromium(II) chloride and iodotrimethylsilane gives the hydroxyalkenyl ethers (III). In most cases, strong predominance of the erythro-isomers is observed. The dibenzyl acetal of crotonaldehyde does not perform this reaction, but decomposes instead.