“…We could now develop an efficient procedure for the formation of five- and six-membered azacycles from the corresponding azidoallene derivatives under neutral conditions. However, we were still interested in the base-catalyzed ring-closing reaction of carbamoylallene compounds . Thus, by analogy to the preparation of the aforementioned allenes (in Schemes and ), the required carbamoylallene derivatives 38 were prepared in a straightforward manner as depicted in Scheme .…”
A new procedure for constructing monocyclic five- and six-membered azacycles by the endo-mode ring-closing reaction of allenylazido derivatives under neutral conditions has been developed. The azabicyclo[m.n.0] compounds were prepared by applying this newly developed procedure. The seven-membered azacycle was prepared when the allene possessing an unsubstituted carboxyl amido functionality was submitted to the basic conditions. In addition, indole and quinoline skeletons were synthesized using this procedure.
“…We could now develop an efficient procedure for the formation of five- and six-membered azacycles from the corresponding azidoallene derivatives under neutral conditions. However, we were still interested in the base-catalyzed ring-closing reaction of carbamoylallene compounds . Thus, by analogy to the preparation of the aforementioned allenes (in Schemes and ), the required carbamoylallene derivatives 38 were prepared in a straightforward manner as depicted in Scheme .…”
A new procedure for constructing monocyclic five- and six-membered azacycles by the endo-mode ring-closing reaction of allenylazido derivatives under neutral conditions has been developed. The azabicyclo[m.n.0] compounds were prepared by applying this newly developed procedure. The seven-membered azacycle was prepared when the allene possessing an unsubstituted carboxyl amido functionality was submitted to the basic conditions. In addition, indole and quinoline skeletons were synthesized using this procedure.
“…285 In particular, allenyl sulfoxides 468 and 474, prepared from propargylic alcohols 467 and 472, respectively, contain internal nucleophiles and provide simple access to heterocyclic structures such as spiroketals 470 286 and indoles 475 (Scheme 81). 287 Within the same context, allenyl sulfoxides can undergo intramolecular cyclization induced by electrophiles. In particular, Christov and Ivanov reported that enynol 476 is transformed into allenyl sulfoxide 478 through sulfenate−sulfoxide rearrangement of sulfenate 477 by treatment with PhSCl and Et 3 N. Further electrophilic addition of bromine to the allene double bond provided an 87% yield of oxathiolium bromide 479, which underwent ring cleavage by HBr elimination upon refluxing in dichloroethane to generate triene sulfoxide 480 in 61% yield (Scheme 82).…”
Section: [23]-sigmatropic Rearrangement From Propargylic Sulfenatesmentioning
The [2,3]-sigmatropic rearrangement of allylic sulfoxides to allylic sulfenates is a reversible process, generally shifted toward the sulfoxide. In the presence of thiophiles, the sulfenate is trapped, and allylic alcohols are obtained under mild conditions. In most cases, a good transfer of stereochemical information through an ordered transition state is obtained. Furthermore, the ease of coupling this process with other versatile, stereocontrolled reactions has enhanced the usefulness of this protocol. This review aims to provide a comprehensive survey of this rearrangement and its application in the synthesis of natural and bioactive products.
“…On the basis of our earlier work on the inter- and intramolecular addition of alcohols to allene sulfoxides, − Matthew Gray developed a tandem sequence for the construction of highly substituted benzofurans (Scheme 39). …”
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