(3,3)Sigmatropic Ring Expansion of Cyclic Thionocarbonates. IV. Relationship between Ring Size of Cyclic Thionocarbonates and Geometry of Created Double Bond in Medium- and Large-Membered Thiolcarbonates.
[3,3]sigmatropic ring expansion of cyclic thionocarbonates. 13.1 synthesis of medium-membered heterocyclic allenes and synthetic application to antifungal constitutent of Sapium japonicum
thionocarbonates (2i-k) afforded a new type of strained 8-membered heterocyclic allenes (3i-k) in high yields. The MNDO optimized structure of 3i indicated the allenyl moiety was bent and strained. The reactivity of 8-membered cyclic allenes was also examined. Further, using this methodology with a novel application of a SmI2-HMPA reduction of the resulting heterocyclic allene (3n), an antifungal constituent
Wohl-Ziegler bromination of 10-membered thiolcarbonates (3) gave regioselectively 7-bromocyclic thiolcarbonates (4). The structure of 4a was unambiguously established by an X-ray crystallographic analysis.
Synthesis of medium-membered heterocyclic allenes by [3,3]sigmatropic rearrangement and its synthetic application to the antifungal constituent of sapium japonicum
Medium-membered heterocyclic allenes were synthesized by the [3,3]sigmatropic rearrangement of cyclic thionocarbonates. Using this methodology and a novel application of a SmI2-HMPA reduction, an antifungal constituent of Sapium japonicum, methyl 8-hydroxy-5,6-octadienoate, was synthesized.
(3,3)Sigmatropic Ring Expansion of Cyclic Thionocarbonates. IV. Relationship between Ring Size of Cyclic Thionocarbonates and Geometry of Created Double Bond in Medium- and Large-Membered Thiolcarbonates.
Medium- and large-membered cyclic thiolcarbonates containing an (E)- or (Z)-double bond were synthesized by two methods using [3, 3]sigmatropic ring expansion of cyclic thionocarbonates. The [3, 3]sigmatropic ring expansion proceeds exclusively via the transition state bearing the chain tethered in a cis relationship when the cyclic thionocarbonates are 8-membered or smaller. Importantly, the ring size of the cyclic thionocarbonate determines the double bond geometry of the thiolcarbonate.Conversion of the cyclic thiolcarbonates into (E)- or (Z)-allylic sulfides is also described.
[3,3]Sigmatropic ring expansion of cyclic thionocarbonates. 8. highly stereoselective synthesis of (Z- or (E)-double bonds by controlling chairlike-boatlike transition states in the [3,3]sigmatropic rearrangement of 8-membered thionocarbonates
synthesis of (Z)- or (E)-double bonds in 10-membered thiolcarbonates (3) was successfully conducted by controlling the chairlike-boatlike transition states in the [3,3]sigmatropicrearrangement of 8-membered thionocarbonates (2). The geometry of the product appeared to be highly dependent on the substituent pattern in the allylic system of the substrates (1). The 10-membered thiolcarbonates (3) were readily