Photochemical Alkylation of Ketene Dithioacetal S,S-Dioxides. An Example of Captodative Olefin Functionalization

Abstract

Radical alkylation of some ketene dithioacetal S,S-dioxides failed through the tin hydride promoted chain process but was successfully performed through stoichiometric photochemical initiation, either by electron transfer or hydrogen abstraction. In the first case, alkyl radicals were produced from tetralkylstannanes (t-Bu-, i-Pr-, n-Bu-SnR(3)) via radical cation fragmentation, while in the second case these were produced from alkanes (cyclohexane, adamantane) by benzophenone triplet. When bulky radicals (t-Bu, adamantyl) were involved, the addition occurred with complete diastereoselectivity.

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

“…Accordingly, β-cycloalkyl dinitrile 418 was smoothly synthesized in 66% isolated yield starting from cyclohexylidene malononitrile 417 and cyclohexane (see Scheme , path a) . In a related case, ketene thioacetal S , S -dioxides, a class of captodative olefins, were likewise successfully used as radical traps …”

Synthesis of γ-lactols, γ-lactones and 1,4-monoprotected succinaldehydes under moderately concentrated sunlight

“…This is one of the motivations that led us to focus our attention on the potential of photocatalyzed reactions (via hydrogen atom transfer) for chemical synthesis and for carbon-carbon bond formation in particular. [5][6][7] Previous work aimed at the assessment of solar photochemistry as a synthetic method has been recently carried out and promising results by using concentrated solar light have been obtained. 8, 9 Sunlight photoreactors equipped with a parabolic mirror such as SOLFIN (SOLar synthesis of FINe chemicals, Fig.…”

The photomediated reaction of alkynes with cycloalkanes

“…This approach has been used in the reaction of enones with 1,3-dioxolanes, 18 the reaction of enals with dioxolanes and alcohols, 19 and the functionalisation of cycloalkanes with alkenyl nitriles 20 and ketene dithioacetal S,Sdioxides. 21 The mechanistic framework for the process suggests that the use of "catalytic" quantities of the carbonyl compound functioning as the photomediator should be sufficient. However, in practice there are many ways in which this molecule can be diverted from performing the required role and so larger amounts are in general required.…”