Synthesis of Complex Hexacyclic Compounds via a Tandem Rh(II)-Catalyzed Double-Cyclopropanation/Cope Rearrangement/Diels–Alder Reaction

Abstract

Treatment of (E)-1-(methoxymethylene)-1,2,3,4-tetrahydronaphthalene with styryl diazoacetates in the presence of catalytic amounts of the dirhodium complex Rh2(S-DOSP)4 provides a highly enantioenriched hexacyclic product with 10 new stereogenic centers. The transformation proceeds by a cascade sequence starting with a double cyclopropanation of a benzene ring, followed by a Cope rearrangement of a divinylcyclopropane and then an intramolecular Diels–Alder cycloaddition.

Recent advances in metal-catalysed asymmetric sigmatropic rearrangements

“…An impressive study in this chemistry is the tandem reaction between vinyldiazoacetates and allylic C–H bonds, called “combined C–H activation/Cope rearrangement” (CHCR), which was originally explored by the Davies group. 35 Many examples based on this concept have been reported in an enantioselective version, confirming its potential value in organic synthesis. Here, we choose the CHCR reaction of vinyl ethers as the model for a brief introduction, not to summarize all relevant work in this field (Scheme 13).…”

Thermally Induced Denitrogenative Annulation for the Synthesis of Dihydroquinolinimines and Chroman‐4‐imines

“…Cuprisorb resin was purchased from Seachem Laboratory (Madison, GA, USA) and dried in high vacuum before use. 1 Ha nd 13 Representative Procedure for the Preparation of Dihydroquinolinimines (4a-4g, 4k-4o): Preparation of (E)-N-(1-benzyl-7-methoxy-2,3-dihydroquinolin-4(1 H)-ylidene)-4-methylbenzenesulfonamide (4a). As olution of N-benzyl-3-methoxy-N-((1-tosyl-1H-1,2,3-triazol-4-yl)methyl)aniline (50 mg, 0.11mmol) in DMF (6.72 mL) was allowed to react at 120 8Cf or 2h.T hen, the solvent was removed under reduced pressure to afford the crude product, which was purified by silica-gel flash column chromatography on using 5% ethyl acetate in hexane as as olvent system to obtain the desired product 4a (42 mg, 89 %).…”

“…Diazo compounds are popular precursors for the generation of carbene intermediates, [1][2][3][4][5] and transition metal catalysis is commonly used in the preparation of carbenoids from these precursors,i ncluding dirhodium, [6][7][8][9][10][11][12][13] copper, [14][15][16][17] ruthenium, [18][19][20][21] and iron complexes. [22,23] The reactivity of these intermediate metal carbenoids, which are used in av ariety of reactions to synthesize important building blocks, is highly dependento n their chemical stability, which is defined by the electronic properties of the substituent groups.E lectron-withdrawing groups (EWGs)o nt he carbenoid moiety can accelerate the transformation of diazo compounds into carbenoids.…”

Recent Advances in Catalytic Enantioselective Rearrangement

“…In 2014, Davies and co‐workers developed an enantioselective synthesis of hexacyclic compound 64 bearing ten stereocenters by a dirhodium complex Cat‐17 catalyzed reaction of the α‐tetralone‐derived enol ether 62 with styryl diazoacetates 63 . A domino process involving enantioselective double cyclopropanation of the benzene ring/Cope rearrangement of a divinylcyclopropane/intramolecular Diels‐Alder reaction was proposed to account for the outcome of this complexity‐generating reaction (Scheme ) …”