From Hydrindane to Decalin: A Mild Transformation through a Dyotropic Ring Expansion

On the mechanism of the dyotropic expansion of hydrindanes into decalins

A combined computational/experimental approach has revealed key mechanistic aspects in a recently reported dyotropic expansion of hydrindanes into decalins. While computer simulations had already anticipated the need for acid catalysis for making this reaction feasible under the mild conditions used in the laboratory, this work places the dyotropic step not into the reaction flask but at a later step, during the work up instead. With this information in hand the reaction has been optimized by exploring the performance of different activating agents and shown to be versatile, particularly in steroid related chemistry due to the two scaffolds that this reaction connects. Finally, the scope of the reaction has been significantly broadened by showing that this protocol can also operate in the absence of the fused six-member ring.

Synthesis of a New Type of Trans-Decalin Vitamin D Analogue through a Dyotropic Ring Expansion

A new vitamin D analogue with a trans-fused decalin as the CD-ring system and containing a sulphur atom in the side chain has been synthesized in our research group. The obtention of this analogue is based on a recently discovered transformation of hydrindane cores into decalins through a dyotropic ring expansion in very mild conditions.

Easy Access to Polyfunctionalized Chiral Decalins

An unexpected ring expansion that converts hydrindanes into decalins via an unprecedented dyotropic reaction involving a mesylate group has been observed, and this paved the way for easy access to polyfunctionalized chiral decalins. These polyfunctionalized chiral decalins can be very useful building blocks for the synthesis of the thia analogues of many natural compounds. They can also be used in asymmetric catalysis and also in the synthesis of the new analogues of vitamin D with a modified D ring and side chain. The use of chiral sulfoxide ligands for asymmetric catalysis or asymmetric sulfur ylide-mediated epoxidation of carbonyl compounds is a very important topic in the field of organic chemistry, hence our results could be useful to the scientific community.

Stereospecific Ring Contraction of Bromocycloheptenes through Dyotropic Rearrangements via Nonclassical Carbocation-Anion Pairs

Experimental and theoretical evidence is reported for a rare type I dyotropic rearrangement involving a [1,2]-alkene shift, leading to the regio- and stereospecific ring contraction of bromocycloheptenes. This reaction occurs under mild conditions, with or without a Lewis acid catalyst. DFT calculations show that the reaction proceeds through a nonclassical carbocation–anion pair, which is crucial for the low activation barrier and enantiospecificity. The chiral cyclopropylcarbinyl cation may be a transition state or an intermediate, depending on the reaction conditions.

Nickel catalyzed regio- and stereoselective arylation and methylation of allenamides via coupling reactions. An experimental and computational study

A novel Ni-catalyzed regio- and stereoselective condensation of boronic acids/Me₂Zn to allenamides is documented and its potential explored.

A Unifying Synthesis Approach to the C18-, C19-, and C20-Diterpenoid Alkaloids

The secondary metabolites that comprise the diterpenoid alkaloids are categorized into C18, C19, and C20 families depending on the number of contiguous carbon atoms that constitute their central framework. Herein, we detail our efforts to prepare these molecules by chemical synthesis, including a photochemical approach, and ultimately a bioinspired strategy that has resulted in the development of a unifying synthesis of one C18 (weisaconitine D), one C19 (liljestrandinine), and three C20 (cochlearenine, paniculamine, and N-ethyl-1α-hydroxy-17-veratroyldictyzine) natural products from a common intermediate.