Cyclizations perruthenate

The second synthesis of crystalline 43 was reported by Mori as summarized in Scheme 62 [93]. The building block (4.R,5S)-A was prepared by an enzymatic process, while another building block C was synthesized via Sharpless asymmetric epoxidation. Coupling of A with C gave D, which was cyclized under Op-polzer s conditions to give crystalline E. When E was oxidized with Dess-Martin periodinane or tetra(n-propyl)ammonium perruthenate or Jones chromic acid, crystalline 43 was obtained. Swern oxidation or oxidation with 2,2,6,6-tetramethylpiperidin-1 -oxyl of E afforded only oily materials. Accordingly, oxidation of E to 43 must be executed extremely carefully. A synthesis of oily 43 was reported by Gil [94]. 

Permanganate- and perruthenate-promoted oxidative cyclization of hexa-1,5-dienes are usually key steps in the total synthesis of naturally occurring molecules containing tetrahydrofuran rings <04JOC3368>, <04SL1437>, <04TL303>. 

As a further extension, the Kim group very recently developed the aerobic oxidation and [l,5]-hydride transfer/cyclization sequence starting from readily available ortho tertiary amine substituted cinnamyl alcohols 24 (Scheme 4.12). The tetrapropylammonium perruthenate (TPAP) was identified as the competent catalyst for the initial aerobic oxidation of the allylic alcohols. The synthetically useful tetrahydroquinoline derivatives 25 were prepared in moderate yields and high level of enantioselectivity. 

Oxidative isomerization of vinylidenecyclopropanes gives dimethylenecyclopropane aldehydes using tetrapropylammonium perruthenate (TPAP)/4-methylmorpholine A-oxide (NMO) as a catalytic system. A Witkop-Winterfeldt oxidation with ozone has been reported to convert tetrahydropyridoindoles into pyrroloquinolones and cinnolines. Activation of phenol derivatives with a hypervalent iodine reagent has been reported to promote the formation of bicycUc and tricyclic products via a cationic cyclization process (Scheme 64). ... 

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