Intramolecular Hetero Diels−Alder Reactions of α,α’-Dioxosulfines − A New Access to the [3.3.1]-Bicyclic Skeleton

Abstract

Simple transformations of tert‐butylthio‐substituted 1,4‐oxathiin permitted the preparation of oxathiin S‐oxides. These in turn were suitable precursors of corresponding α,α′‐dioxosulfine dienes with tethered internal electron‐rich double bonds. Examining the synthetic utility of these sulfines, we observed either hydrolysis or intramolecular cycloaddition, depending on the distance between the reactive centres and the substitution on the double bond. Bicyclic derivatives with a [3.3.1] skeleton and an sp2 bridgehead carbon were obtained from the cycloadditions.

The Synthesis and Base-Induced Breakdown of Triaryl 1,4-Oxathiins—An Experimental and DFT Study

“…This latter fate is presumed to lead to the undesired breakdown of the product. Variation of the aldehyde reactant created increased variability in the isolated yields (Table 1 # [11][12][13][14][15][16][17]. Heterocyclic furfural and thiophene-2-carboxaldehyde gave reduced yields (#17, 20); pyridine-2-carboxaldehyde did not yield any cyclized products.…”

“…The 1,4-oxathianes and -oxathiins have also been sought for access to acyclic targets [15,16] and as precursors to other heterocycles [17][18][19][20][21][22]. An oxathiin is an important component in a total synthesis of (+)-solamin [22].…”

“…An oxathiin is an important component in a total synthesis of (+)-solamin [22]. The general heterocyclic ring system has been prepared through condensation-based [23] and other cyclization protocols [2,14,[24][25][26][27][28], through the intermediacy of sulfenic acids [29], by cycloaddition chemistry [17,18,[30][31][32][33], by multicomponent protocols [34] and through ring expansion of other heterocycles including sulfolene [35], 1,3-oxathiolanes [2,[36][37][38] or oxetanes [39].…”

“…The result is a collection of 1,4-oxathiins with four substituents around the ring, and the 2,3-groups can be placed with high diastereoselectivity. Also interesting is the thermal chemistry of the sulfoxide form of the 2-alkoxy substituted oxathiins, which undergo a retro-Diels-Alder reaction when heated [17,18,32]. The electrondeficient oxosulfine so formed can be re-captured via a hetero-Diels-Alder reaction to generate alternative 1,4-oxathiins 4-oxides [18,30].…”

“…The electrondeficient oxosulfine so formed can be re-captured via a hetero-Diels-Alder reaction to generate alternative 1,4-oxathiins 4-oxides [18,30]. The 1,4-oxathianes and -oxathiins have also been sought for access to acyclic targets [15,16] and as precursors to other heterocycles [17][18][19][20][21][22]. An oxathiin is an important component in a total synthesis of (+)-solamin [22].…”