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The daphnezomine A‐type subfamily of Daphniphyllum alkaloids structurally features a unique aza‐adamantane core skeleton and anticipates efficient strategies for completing their syntheses to thoroughly investigate their biological activities. Herein, divergent total syntheses of (−)‐daphnezomines A and B and (+)‐dapholdhamine B have been accomplished in 16–20 steps from a known epoxide via rapid construction of a common core intermediate. The present work features a Ti‐mediated radical cyclization to establish the azabicyclo[3.3.1]nonane ring system, an intramolecular Heck reaction to install the bridgehead all‐carbon quaternary stereocenter, a tandem deprotection/reduction/keto amine‐carbinolamine tautomerization to furnish the aza‐adamantane backbone, and an NIS‐promoted 6‐endo‐trig aminocyclization to assemble the (+)‐dapholdhamine B backbone. [ABSTRACT FROM AUTHOR]

An array of spiro[benzofuran-2,3′-pyrazol]-3-imines with diverse functional groups were readily assembled from aurone-derived azadienes and in - situ generated nitrilimines under mild conditions. The transformation was performed in a regio- and diastereoselective fashion, in which a synergetic [2+3] cycloaddition pathway was likely involved. This novel methodology has extended the synthetic application of aurone-derived azadienes as a kind of two-atom synthon. [ABSTRACT FROM AUTHOR]

An efficient, one-pot, three-component [3+2] cycloaddition reaction of azomethine ylide obtained from α-dicarbonyl compounds (cyclic and acyclic diketone or keto ester) and amino acids with maleimides under catalyst-free conditions has been developed. This cascade protocol shows high efficiency and remarkable functional group tolerance, and the ubiquitous succinimide-fused pyrrolizidines with a highly compact and strained scaffold were obtained with high yield and excellent diastereoselectivity. Furthermore, this novel and atom-economical strategy could be performed on a gram scale with comparable reaction efficiency. [ABSTRACT FROM AUTHOR]

The synthesis of pyridothiazepines has been achieved via a 1,5‐dipolar cycloaddition reaction between pyridinium 1,4‐zwitterionic thiolates and activated allenes conducted under thermal conditions. Meanwhile, a ring‐contraction reaction of the resulting pyridothiazepine derivatives via the extrusion of 3‐thioxoacrylates has also been described. [ABSTRACT FROM AUTHOR]

A cobalt-catalyzed direct C–H/N–H functionalization of thiophene-2-carbohydrazides with maleimides by utilizing 2-(1-methylhydrazinyl)pyridine (MHP) as an easily removable bidentate directing group has been developed. This formal [4+2] cycloaddition has been achieved for the first time, and it provides an alternative and versatile approach to construct thiophene-fused pyridones using an inexpensive cobalt catalyst. The C–H/N–H activation cascade protocol showed a high efficiency and a broad substrate scope, and the products were obtained in good to excellent yields. [ABSTRACT FROM AUTHOR]

We have developed a unique approach for the thermally promoted cycloaddition of cyclohexadienone-tethered allenes to form a versatile cyclobutane-fused oxygen-containing tricyclic framework in an environmentally friendly and atomic economic fashion with high regioselectivity. The reaction encompasses a broad substrate scope and functional group tolerance of cyclohexadienone moieties. Moreover, the cycloaddition was also applicable to the late-stage functionalization of pharmaceutically relevant compounds. [ABSTRACT FROM AUTHOR]

A cobalt‐catalyzed direct C−H/N−H functionalization of benzoyl hydrazide with isocyanide by utilizing 2‐(1‐methylhydrazinyl)pyridine (MHP) as a bidentate directing group has been developed. This formal [4+1] cycloaddition protocol showed high efficiency and remarkable functional group tolerance, and the ubiquitous 3‐iminoisoindolinones were obtained in good to excellent yields in the presence of the earth‐abundant cobalt catalyst. Moreover, this transformation was accomplished by employing environmentally friendly oxygen as the sole oxidant in the absence of any other additives. [ABSTRACT FROM AUTHOR]

A general and efficient protocol was developed for the synthesis of polysubstituted pyridines from propargyl amines and unsaturated carbonyl compounds through a tandem condensation/alkyne isomerization/6π 3‐azatriene electrocyclization sequence. This process was found to be applicable to a wide range of readily available substrates (30 examples, up to 95 % yield) and could be readily performed on a preparative (20 g) scale. By taking advantage of this method for late‐stage pyridine incorporation, we successfully completed the collective total synthesis of suveoline, norsuveoline, and macrophylline. 6π to py: A wide range of polysubstituted pyridines were synthesized in a straightforward manner from propargyl amines and unsaturated aldehydes through a tandem condensation/alkyne isomerization/6π 3‐azatriene electrocyclization sequence in good yields. This transformation was used as a key step in the collective total synthesis of suveoline, norsuveoline, and macrophylline (see scheme). [ABSTRACT FROM AUTHOR]

Abstract: A unified protocol for the construction of 6H‐benzofuro[2,3‐b]indoles and 5,6‐dihydroindolo[2,3‐b]indoles via UV light‐mediated diradical cyclization was developed and preliminary efforts were also made to functionalize at C10b position of 6H‐benzofuro[2,3‐b]indoles. This mild and facile strategy may have great potential in the syntheses of natural products and functional materials. [ABSTRACT FROM AUTHOR]

Abstract: (−)‐Daphnilongeranin B and (−)‐daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (−)‐daphnilongeranin B and a bioinspired synthesis of (−)‐daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late‐stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline. [ABSTRACT FROM AUTHOR]

Rhodium-catalyzed denitrogenative [3+2] cycloaddition of 1-sulfonyl-1,2,3-triazoles with cyclic silyl dienol ethers has been developed for the synthesis of functionalized hydroindolones or their corresponding silyl ethers. The present method has been employed to construct synthetically valuable bicyclo[3.3.1]alkenone derivatives and pyrrolidine-ring-containing bicyclic indole compounds. As a further synthetic application, a stereoselective synthesis of 5,11-methanomorphanthridin-3-one, which shares a key skeleton with montanine-type Amaryllidaceae alkaloids has been achieved by using this chemistry. [ABSTRACT FROM AUTHOR]

Described herein is the first asymmetric total synthesis of (+)-harringtonolide, a natural diterpenoid with an unusual tropone imbedded in a cagelike framework. The key transformations include an intramolecular Diels-Alder reaction and a rhodium-complex-catalyzed intramolecular [3+2] cycloaddition to install the tetracyclic core as well as a highly efficient tropone formation. [ABSTRACT FROM AUTHOR]

An efficient synthetic route toward the highly congested [5-6-7] tricyclic core of calyciphylline A-type alkaloids has been developed. This approach features a highly efficient intramolecular Diels-Alder cycloaddition to establish the aza-five-membered C ring as well as the C1 all-carbon quaternary center, and a subsequent cyclopropanation together with a ring-expansion reaction of the resulted adduct to construct the seven-membered D ring. [ABSTRACT FROM AUTHOR]

An efficient synthesis of an oxo-bridged 7/6-bicyclic precursor that is potentially useful for the construction of harringtonolide has been realized through a [4+3] cycloaddition reaction. Meanwhile, an unexpected rearrangement reaction, which could be used for the fast assembly of spirocycles, was found during the double elimination attempts. [ABSTRACT FROM AUTHOR]

A fused 6,6,5-tricyclic difluorinated nicotine analogue was efficiently assembled in five steps in 36% overall yield. The conformation-restricting unit is a six-membered fluorinated carbocycle. The gem-difluoromethylene group was introduced through an indium-promoted Barbier allylation of 3-bromo-3,3-difluoropropene. The construction of the tricyclic skeleton was achieved using an intramolecular azomethine ylide-alkene [3+2] cycloaddition. [ABSTRACT FROM AUTHOR]

Abstract: Racemic nonactic acid was efficiently constructed in a convergent, stereocontrolled fashion (7 steps, 27%). The present synthesis features a stereocontrolled 1,3-dione reduction with NaBH4/Et2B(OMe) and an acid-promoted stereospecific cyclization in the formation of 7. [Copyright &y& Elsevier]

Thefirst total synthesis of the (±)-sculponeatin N (a 6,7-seco-ent-kaurane diterpenoid discoveredby Sun and co-workers) has been achieved. The features include a regio-and stereoselective aldol reaction to form a lactone, an intramolecularDiels–Alder reaction to install B and C rings simultaneously,and a radical cyclization to forge the D ring. [ABSTRACT FROM AUTHOR]

Abstract: We describe the synthesis of a series of conformationally constrained nicotine analogues 2–5 from appropriate pyridine-containing enals, featuring an intramolecular azomethine ylide–alkene [3+2] cycloaddition. The objective of the current project is to develop new selective nAChRs-targeting ligands. Of the nicotine analogues that we have studied, the conformation-restricting ring B unit can be either a five-membered carbocycle, or a six-membered carbocycle or heterocycle. The present work constitutes a general method for rapid assembly of other related tricyclic nicotine analogues. [Copyright &y& Elsevier]

A 1,3-dipolar cycloaddition reaction of arynes with 3-diazoindolin-2-ones under mild conditions in excellent yields has been developed, which allows facile access to a library of labile spiro[indazole-3,3′-indolin]-2′-ones. Spiro[indazole-3,3′-indolin]-2′-imines could be obtained as well following the same protocol. The isomerization reaction of spiro[indazole-3,3′-indolin]-2′-ones under thermal or acidic conditions has been efficiently achieved to afford a wide range of indazolo-[2,3- c quinazolin-6(5H)-ones and the one-pot synthesis of indazolo-[2,3- c quinazolin-6(5H)-ones from arynes and 3-diazoindolin-2-ones is also described. Whereas, spiro[indazole-3,3′-indolin]-2′-imines could not undergo the same rearrangement. Image 1 • aSpiro[indazole-3,3'-indolin]-2'-ones and spiro[indazole-3,3'-indolin]-2'-imines could be obtained via 1,3-dipolar cycloaddition reactions of arynes. • c The isomerization reactions of spiro[indazole-3,3'-indolin]-2'-ones under thermal or acidic conditions have been achieved to afford indazolo-[2,3- c quinazolin-6(5H)-ones. • c One-pot synthesis of indazolo-[2,3- c quinazolin-6(5H)-ones from arynes and 3-diazoindolin-2-ones is extensively studied. [ABSTRACT FROM AUTHOR]

A cascade consisting of a Wittig reaction, a Staudinger reaction between propargyl azide and triphenylphosphine followed by an aza-Wittig reaction with subsequent 6π-3-azatriene electrocyclization and 1,3-H shift furnishes polysubstituted pyridines. [ABSTRACT FROM AUTHOR]

A highly efficient intramolecular Diels-Alder cycloaddition for the establishment of the aza-five-membered ring and the C-1 quaternary center is the key step for the construction of the title tricyclic core, followed by cyclopropanation together with a ring-expansion for the construction of the seven-membered ring. [ABSTRACT FROM AUTHOR]