Preparation of seven and larger membered heterocycles by electrophilic heteroatom cyclization

1,2,4,5-Tetraoxacycloalkanes: Synthesis and Antimalarial Activity

“…The key is the efficient intramolecular trapping of the derived carbonyl oxide intermediate by the remote hydroperoxy group, which is assisted by AcOH or trifluoroethanol, protic solvent with a low nucleophilicity [16]. Thus, ozonolysis of peracetal 16a in AcOH-CH 2 Cl 2 provides the hydroperoxy-substituted 1,2,4,5-tetroxocane 26, which is readily methylated using methyl iodide in the presence of Ag 2 O to yield 27 (Scheme 6) [13].…”

7-endo selenocyclization reactions on chiral 3-prenyl and 3-cinnamyl-2-hydroxymethylperhydro-1,3-benzoxazine derivatives. A way to enantiopure 1,4-oxazepanes

“…On the other hand, the double substitution at the terminal double bond in prenyl derivatives can have a negative effect due to the increase of steric hindrance which disfavoured the formation of 7-membered rings. 17 Interesting, the diastereoselectivity in the endo path-way was dependent on both the reaction conditions and the nature of the hydroxyl group. Nevertheless, the nature of the substituents at the double bond has less influence.…”

“…15 The electrophile-mediated cyclofunctionalization of alkenes containing and internal nucleophile 16 is an useful cyclization reaction for the preparation of heterocyclic compounds and seven-membered compounds have been synthesized in good yields in this way by a proper choice of the electrophilic reagents and the substituents at the double bond. 15h, 17,18 In a previous paper, we have described the regio-and diastereoselective methoxyselenenylation of chiral 2-vinyl 19 and 3-allylperhydro-1,3-benzoxazines 20 and the synthesis of enantiopure morpholine derivatives by selenocyclofunctionalization 21,22 of chiral 3-allyl-2-hydroxymethyl substituted perhydro-1,3-benzoxazine derivatives. , 23 In most cases, 3-allyl-2-hydroxymethylperhydro-1,3-benzoxazine derivatives cyclized in an 6-exo mode with total regioselectivity to the morpholine ring in the presence of benzeneselenenyl chloride.…”

Development of a General, Sequential, Ring-Closing Metathesis/Intramolecular Cross-Coupling Reaction for the Synthesis of Polyunsaturated Macrolactones

“…The carbon-heteroatom-based cyclization to build macrolactams and macrolactones was reported first and since then, many reports of hydroxy acid lactonization or amino acid lactamization that use different activating groups have been developed 13. In addition, lactone formation via a π-allylpalladium intermediates has been reported 14. Cyclization via a carbon-carbon based strategy initially began with nucleophile- and electrophile-promoted methods,9 and later radical and metal-catalyzed cyclizations appeared 15.…”

“…Among the earliest reports of a palladium-catalyzed macrocyclization was the palladium-catalyzed intramolecular alkylation of π-allylpalladium complexes with sulfone-stabilized anions 24. The reaction affords medium- to large-ring macrolactones in good yields and has been applied as the key step in total synthesis of natural products25 Other reports of nucleophilic addition to π-allylpalladium complexes to form macrocycles and macrolactone natural product have appeared 14…”