Studies toward the synthesis of natural and unnatural dienediynes 1. Approaches to a functionalised bicyclic ring system

Chemistry of 4‐Hydroxy‐2‐cyclopentenone Derivatives

“…[17] Caddick et al improved this sequence as follows: under oxidative conditions (mCPBA or NBS) followed by basic conditions (sodium acetate in acetic anhydride), furfuryl alcohols 39 were converted via the dihydrofuran 40 and the ring opened intermediate 41 into the target pyranones 42 in good yield. [18] Transacetalisation provided the corresponding tert-butyl derivatives 43, which proved to be the substrates of choice for the subsequent skeletal rearrangement, in which the enolate 44 underwent retro-6π-electrocyclisation to give 45 followed by vinylogous aldolisation to deliver the 5,5-disubstituted 4-tert-butoxy-2-cyclopentenones 46. This single-step transformation from 43 proved to be highly diastereoselective, presumably due to the bulkiness of the tert-butyl group.…”

“…This single-step transformation from 43 proved to be highly diastereoselective, presumably due to the bulkiness of the tert-butyl group. [18] Scheme 5.…”

Halogenated Oxabicyclo[3.2.1]octadiene Building Blocks: Elaboration of the Dibromoenone

“…A vinylogous Finkelstein reaction [6] occurred in excellent yield by heating 2 with sodium iodide in acetone. Morpholine reacted in very high yield to give the vinylogous amide 3b while cyanide added in much lower yield to give the nitrile 3c.…”

“…138-140°C. 1 H NMR (500 MHz, CDCl 3 ): δ = 7.07 (dd, J = 2.0, 0.7 Hz, 1 H), 6.57 (ddd, J = 5.9, 2.4, 0. : To a 25 mL round-bottomed flask was added compound 2 (200 mg, 0.72 mmol).…”

Chemistry of Propargyldicobalt Cations Recent Developments in the Nicholas and Related Reactions

“…Finally, Caddick has prepared more highly oxygenated versions of the bicyclo [7.3.0]core of the neocarzinostatin and kedarcidin class of enediynes via boron mediated aldol type closure on an alkynal-Co 2 (CO) 6 complex [100]. …”