Cyclizations 2-iodoxybenzoic acid

Lindel and co-workers had earlier achieved cyclization of intermediate 166 with 2-iodoxybenzoic acid (IBX, Dess-Martin periodinane) to give 167 (Equation 41), followed by subsequent dehydration and dihydroxylation of G(10)—C(10zz) to an advanced synthetic intermediate <2002TL3699>. 

Exposure of unsaturated anilides to o-iodoxybenzoic acid in THF-DMSO at 90°C results in cyclization to give y-lactams [Eq. (88)] [163]. A mechanism involving an intermediacy of amidyl radical 95, produced by SET and then deprotonation, was proposed for the formation of y-lactams. 

Organohypervalent iodine reagents such as iodoxybenzene, o-iodoxybenzoic acid (IBX), bis(trifluoroacetoxy)iodobenzene (BTI), and Dess-Marhn periodinane have been used for the oxidation of alcohols and phenols. Most of these reactions are conducted in high-boiling DMSO or relahvely toxic acetonitrile, which increase the burden on the environment. Further, the use of inexpensive iodobenzene diacetate (IBD) as an oxidant has not been fully exploited. Varma et al. have reported the first use of supported iodobenzene diacetate as an oxidant. In this novel oxidative protocol, alumina-supported IBD under solvent-free conditions rapidly converts alcohols to the corresponding carbonyl compounds in almost quantitative yields. The use of alumina as a support improved the yields markedly as compared to neat IBD (Scheme 2.2-40). 1,2-Benzenedimethanol, however, undergoes cyclization to afford l(3H)-isobenzofuranone [116]... 

The total synthesis of the natural chromone pestalotiopsone A includes a microwave-promoted aldol condensation and oxa-Michael cyclization to construct the chromanone core, followed by 2-iodoxybenzoic acid (IBX)-induced dehydrogenation to afford the desired chromone. The synthesis of pestalotiopsones B, C, and F is also accomplished using similar approaches (13OBC1109). 1,3,5-Trimethoxybenzene is the starting material for the... 

Related isoflavones have been prepared, using SPOS, by Harikrishnan and Showalter. Resin-bound salicyl aldehyde derivatives 336, immobilized via a traceless silyl linker unit, were prepared and treated with a Grignard reagent to introduce the first point of diversity. Subsequent re-oxidation with 2-iodoxybenzoic acid (IBX), and deprotection of the methoxymethyl (MOM) group provided ketone 338. Treatment of ketone 338 with amide acetals promoted an unusual cyclization, which concurrently installed R to give 339. Final traceless cleavage with CsF or TBAF releases isoflavones 340 (Scheme 3.59). 

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