Total Syntheses of (±)-(Z)- and (±)-(E)-9-(Bromomethylene)-1,5,5-trimethylspiro[5.5]undeca-1,7-dien-3-one and (±)-Majusculone

Abstract

Total Syntheses of (±)-(Z)-and (±)-(E)-9-(Bromomethylene)-1,5,5-trimethylspiro[5.5]undeca-1,7-dien-3-one and (±)-Majusculone Abstract: A new total synthesis of the chamigrene sesquiterpenoids (Z)-9-(bromomethylene)-1,5,5-trimethylspiro[5.5]undeca-1,7-diene-3-one and its 15-E-epimer has been accomplished in 13 steps. In our sequence, a Diels-Alder reaction and subsequent reductive alkylation of the resulting adduct was utilized as the key strategy to create the A-ring and the quaternary spirocenter with the suitable functionalities for accessing the B-ring. Additionally, from the advanced intermediate, a total synthesis of (±)-majusculone, a nor-chamigrene natural product, was also readily achieved in two steps.

Access to Diverse Seleno-spirocyclohexadienones via Ag(II)-Catalyzed Selenylative ipso-Annulation with Se and Boronic Acids

“…The Ag­(II)-catalyzed oxidative selenylative ipso -annulation was further expanded to the biaryl ynones holding 4-OMe group on distal phenyl ring to obtain spiro[5.5]­trienones (Scheme ). The spiro[5.5]­trienones are key structural motifs present in diverse biologically active molecules. , To best of our knowledge, there are only two methods available in the literature to access selenylated spiro[5.5]­trienones using diselenide as selenium source. , Hence, the present protocol employing Se powder in the presence of boronic acid will be attractive for the assembly of various seleno-spiro[5.5]­trienones. Agreeably, the reaction of 6a with phenyl boronic acid ( 2a ) under the optimal reaction conditions led to seleno-spiro­[5,5]­trienone 7a in 90% yield.…”

“…The spiro[5.5]trienones are key structural motifs present in diverse biologically active molecules. 16 , 17 To best of our knowledge, there are only two methods available in the literature to access selenylated spiro[5.5]trienones using diselenide as selenium source. 15b , 18 Hence, the present protocol employing Se powder in the presence of boronic acid will be attractive for the assembly of various seleno-spiro[5.5]trienones.…”

Synthesis and Reactivity Profile of Ylidenemalononitrile Enamines and Their Ester Analogs Towards Electrophiles and Nucleophiles

“…Prepared according to the general procedure with some modifications . To a 20 mL microwave vial was added LiBr (2.61 g, 30 mmol, 3 equiv), acetone (15 mL, 204 mmol, 20.4 equiv), methyl cyanoacetate (0.9 mL, 10 mmol, 1 equiv), and powdered 5 Å molecular sieves (1.5 g) with a stir bar.…”

Electrochemical Selenylative Carbannulation of Biaryl Ynones to Seleno-Dibenzocycloheptenones/Spiro[5.5]Trienones

“…Dibenzocycloheptane is a key structural motif, frequently encountered in biologically active natural products and pharmaceutical compounds. − For instance, naturally occurring allocolchicine (Figure A) and related derivatives such as N -acetylcolchinol (Figure B) and its methyl ether (NSC 51046) as well as its dihydrogenphosphate (ZD 6126) holding a dibenzocycloheptane (6-7-6 carbocyclic) skeleton are exhibiting promising tubulin binding activity toward the treatment of different types of cancers. Similarly, the spirocyclic frameworks, especially spiro­[5,5]­trienones, are not only employed as valuable intermediates in organic synthesis and medicinal chemistry but also frequently found as important structural components in bioactive natural products, , such as pulchelstyrene (Figure C) and laurencenone (Figure D).…”