Rh(II)-Catalyzed Transannulation of <i>N</i>‑Sulfonyl-1,2,3-Triazoles with 2,1-Benzisoxazoles or 1,2-Benzisoxazoles

A Rh­(II)-catalyzed transannulation of <i>N</i>-sulfonyl-1,2,3-triazoles with 2,1-benzisoxazoles has been developed, which affords an efficient method for the synthesis of quinazoline derivatives. The transformation represents an unprecedented example which utilizes <i>N</i>-sulfonyl-1,2,3-triazole as an aza-[2C]-component in cycloadditions. Meanwhile, a Rh­(II)-catalyzed formal [3 + 2] cycloaddition of <i>N</i>-sulfonyl-1,2,3-triazoles with 1,2-benzisoxazoles is also presented, which enables the rapid synthesis of functionalized imidazole derivatives

Asymmetric Total Synthesis of Dragonbloodins A1 and A2

The first asymmetric total synthesis of dragonbloodins A1 and A2, a pair of unprecedented chalcone-flavan heterotrimmers, has been achieved through a series of rationally designed or bioinspired transformations. Key elements of the synthesis include a highly efficient heterotrimerization reaction to assemble the two chalcone units and one flavan unit in one pot and a tandem oxidative dearomatization/cyclization/oxygenation reaction to forge the polycyclic core of dragonbloodins A1 and A2. The present synthesis unambiguously confirms the biogenetic relationship and absolute stereochemistry of dragonbloodins A1 and A2

Biomimetic Syntheses of Rubialatins A, B and Related Congeners

The first total syntheses of rubialatins A and B, two newly discovered naphtho­hydro­quinone dimers, were achieved with high efficiency and elegancy through rationally designed biomimetic approaches. The tandem ring contraction/Michael addition/aldol reaction followed by oxidation enabled the rapid access of prerubialatin from readily available precursors, which then diverted into rubialatins A and B via epoxidation and photoinduced skeletal rearrangement, respectively. Moreover, several new rubialatin congeners were also obtained along the synthetic tour, some of which were proved to be authentic natural products

Rhodium(II)-Catalyzed Formal [3 + 2] Cycloaddition of <i>N</i>‑Sulfonyl-1,2,3-triazoles with Isoxazoles: Entry to Polysubstituted 3‑Aminopyrroles

A novel rhodium­(II)-catalyzed formal [3 + 2] cycloaddition of <i>N</i>-sulfonyl-1,2,3-triazoles with isoxazoles has been achieved that provides an efficient method for the synthesis of polysubstituted 3-aminopyrrole derivatives. An operationally simple one-pot synthesis of the titled compounds from terminal alkynes, tosyl azide, and isoxazoles was also developed. The presented reaction affords an illustrative example of employing 1,2,3-triazoles as the [2C]-component in relevant cycloaddition reactions

Enantioselective Total Syntheses of (+)-Hippolachnin A, (+)-Gracilioether A, (−)-Gracilioether E, and (−)-Gracilioether F

The <i>Plakortin</i> polyketides represent a structurally and biologically fascinating class of marine natural products. Herein, we report a unified strategy that enables the divergent syntheses of various <i>Plakortin</i> polyketides with high step-economy and overall efficiency. As proof-of-concept cases, the enantioselective total syntheses of (+)-hippolachnin A, (+)-gracilioether A, (−)-gracilioether E, and (−)-gracilioether F have been accomplished based on a series of bio-inspired, rationally designed, or serendipitously discovered transformations, which include (1) an organocatalytic asymmetric 1,4-conjugate addition to assemble the common chiral γ-butenolide intermediate enroute to all of the aforementioned targets, (2) a challenging biomimetic [2+2] photocycloaddition to forge the oxacyclobutapentalene core of (+)-hippolachnin A, (3) a [2+2] photocycloaddition followed by one-pot oxidative cleavage of methyl ether/Baeyer–Villiger rearrangement to access (−)-gracilioether F, and (4) an unprecedented hydrogen-atom-transfer-triggered oxygenation of vinylcyclobutane to afford (+)-gracilioether A and (−)-gracilioether E in one pot

Enantioselective Biomimetic Total Syntheses of Katsumadain and Katsumadain C

Enantioselective total syntheses of katsumadain and katsumadain C were achieved concisely through a biomimetic approach. Assembly of styryl-2-pyranone (<b>3</b>) and monoterpene <b>6</b> via acid-promoted regio- and stereoselective C–C bond formation afforded katsumadain (<b>2</b>), which underwent the photoinduced [2 + 2] dimerization in a head-to-tail mode to furnish katsumadain C (<b>1</b>)

Enantioselective Total Syntheses of (+)-Hippolachnin A, (+)-Gracilioether A, (−)-Gracilioether E, and (−)-Gracilioether F

The <i>Plakortin</i> polyketides represent a structurally and biologically fascinating class of marine natural products. Herein, we report a unified strategy that enables the divergent syntheses of various <i>Plakortin</i> polyketides with high step-economy and overall efficiency. As proof-of-concept cases, the enantioselective total syntheses of (+)-hippolachnin A, (+)-gracilioether A, (−)-gracilioether E, and (−)-gracilioether F have been accomplished based on a series of bio-inspired, rationally designed, or serendipitously discovered transformations, which include (1) an organocatalytic asymmetric 1,4-conjugate addition to assemble the common chiral γ-butenolide intermediate enroute to all of the aforementioned targets, (2) a challenging biomimetic [2+2] photocycloaddition to forge the oxacyclobutapentalene core of (+)-hippolachnin A, (3) a [2+2] photocycloaddition followed by one-pot oxidative cleavage of methyl ether/Baeyer–Villiger rearrangement to access (−)-gracilioether F, and (4) an unprecedented hydrogen-atom-transfer-triggered oxygenation of vinylcyclobutane to afford (+)-gracilioether A and (−)-gracilioether E in one pot

Carbene-Catalyzed Enantioselective Petasis-Like Alkenylation

The N-heterocyclic carbene (NHC)-catalyzed enantioselective Petasis-like alkenylation of o-hydroxycinnamaldehydes or hydroxyl-tethered α,β-unsaturated aldehydes with styryl, dienyl, or trienyl boronic acids is disclosed. This method involves the addition of π-system-containing boronic acids to NHC-bounded α,β-unsaturated acyl azoliums and allows access to divergent assembly of β-alkenyl substituted dihydrocoumarin and γ- and δ-lactones. DFT calculations suggest that an unprecedented zwitterionic intermediate and 1,4- or 1,5- migration of alkenyl groups play a crucial role in the reaction. More in-depth studies of orbital and noncovalent interaction analysis provide more detailed explanations for pathways and stereoselectivity control

Carbene-Catalyzed Enantioselective Petasis-Like Alkenylation

The N-heterocyclic carbene (NHC)-catalyzed enantioselective Petasis-like alkenylation of o-hydroxycinnamaldehydes or hydroxyl-tethered α,β-unsaturated aldehydes with styryl, dienyl, or trienyl boronic acids is disclosed. This method involves the addition of π-system-containing boronic acids to NHC-bounded α,β-unsaturated acyl azoliums and allows access to divergent assembly of β-alkenyl substituted dihydrocoumarin and γ- and δ-lactones. DFT calculations suggest that an unprecedented zwitterionic intermediate and 1,4- or 1,5- migration of alkenyl groups play a crucial role in the reaction. More in-depth studies of orbital and noncovalent interaction analysis provide more detailed explanations for pathways and stereoselectivity control

Total Synthesis of Incarvilleatone and Incarviditone: Insight into Their Biosynthetic Pathways and Structure Determination

A concise biomimetic total synthesis of incarvilleatone and incarviditone is achieved in one pot via the highly stereoselective hetero- and homodimerization of (±)-rengyolone, respectively. The structure of incarviditone is revised on the basis of spectroscopic and computational evidence