W-CPBA

Conditions (a) 1-5 mol% catalyst, w-CPBA/NMO, -78°C, CH2CI2. (b) 1-5 mol% catalyst, NaOCl, 4-phenylpyridine iV-oxide, 0°C, CH2CI2. (c) 1-5 mol% catalyst, NaOCl, pyridine iV-oxide, 0°C, CH2CI2. (d) Solvent = diethyl ether... 

Minisci reactions have also been applied to these compounds. formation by exposure to w-CPBA and O-methylation with Meerwein s reagent converted 54 into 55. Nucleophilic attack of the hydroxymethyl radical, generated with ammonium sulfate, provides an alternate route to 2-hydroxymethyl pyridines 56. 

OxiddQon of oximes to rutro compounds with w-CPBA has been applied to the synthesis of dialkyl l-nitroalkanephosphonates fEq 2 63, which are useful reagents for d carbonyl compounds to nitroalkenes... 

In the original patent published by Merck in 1995, rofecoxib (2) was synthesized in three steps from the known 4-(methylthio)acetophenone (10), prepared from the Friedel-Crafts acylation of thioanisole. As depicted in Scheme 2, oxidation of sulfide 10 using an excess of magnesium monoperoxyphthalate hexahydrate (MMPP, an inexpensive, safe and commercially available surrogate for w-CPBA) gave rise to sulfone 11, which was subsequently brominated with bromine and AICI3 to afford 2-bromo-l-(4-(methylsulfonyl)phenyl)ethanone (12). After recrystallization from 1 1 EtOAc/hexane, the pure phenylacyl bromide 12 was then cyclo-condensed with phenylacetic acid under the influence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to deliver rofecoxib (2) in... 

In the following epoxidation step, m /a-chlorobenzoic acid (w-CPBA) has the choice to attack the 10,11-double bond or the 13,14-double bond. Because a hydrogen bond between the alcohol at C-9 and the peracid stabilizes the transition state 80, only the 10,11-double bond is epoxidized. In addition, this hydrogen bond also directs the attack to come from the same side as the alcohol and thus leads to a high substrate-controlled stereoselectivity. 

Another effective iodination method is the treatment of thienotrifluoroborates and ben-zothienotrifluoroborates with sodium iodide and an oxidant [32], Thus, 3-thienotrifluo-roborate 23 and 2-benzothienotrifluoroborate 25, derived from their corresponding boronic acids, were converted to their iodo adducts 24 and 26 in the presence of sodium iodide and chloramine-T in aqueous THF in 83 and 72% yields, respectively. Other oxidants such as w-CPBA and hydrogen peroxide delivered the predicted products however, the yields were significantly lower. 

An interesting case of N-oxidation is given by [2.2](2.5)furano(3,6)py-ridazinophane (67). Oxidation with w-CPBA gave the chiral N-oxide 68 together with a smaller amount of diketone 69, resulting from furan ring... 

The Rubottom oxidation1 is the peracid-mediated oxidation of trimethylsilyl enol ethers to afford a-silyloxy- or a-hydroxy aldehydes or ketones.2,3 Use of an aqueous workup generally affords the hydroxy compounds, whereas nonaqueous workups provide the silyloxy derivatives. For example, the enolsilane 1 derived from cycloheptanone was converted to 2 in 77% yield by treatment with /w-CPBA followed by workup with 10% aqueous sodium hydroxide. Omission of the aqueous workup afforded 3 in 85% isolated yield,1 ... 

The first examples of enolsilane oxidations were described independently by Brook,lb Hassner,lc and Rubottom in late 1974-early 1975. Brook reported that oxidation of enolsilanes derived from cyclic and acyclic ketones with w-CPBA affords a-silyloxy ketones in good yields subsequent hydrolysis of these products provided the corresponding alcohols. Rubottom noted that either a-silyloxy ketones or a-hydroxy ketones could be obtained depending on the nature of the workup (nonaqueous vs. aqueous). Hassner observed that enolsilanes derived from both aldehydes and ketones are suitable substrates for these transformations. Subsequent studies by Rubottom and others led to significant expansions of this methodology along with a more complete understanding of the mechanism of these reactions.2,3... 

A double hydroxylation of enolsilanes under modified Rubottom oxidation conditions has been developed by Nakamura and Kuwajima.20 As shown below, treatment of enolsilane 40 with w-CPBA in the presence of excess KHCO3 generates doubly oxidized product 41 in 72% yield. The mechanism of these transformations is believed to involve elimination/epoxide opening of the intermediate silyloxyoxirane 42 followed by a second oxidation of the resulting enolsilane 43. 

For the (salen)mangancse(lll). w-CPBA, it seems that no mechanistic studies had been published before our works (see below). In this Chapter, we have combined our recent HPR and NMR spectroscopic findings on both the (salcn)manganesc(lll)/PhlO and (salen)mangancsc(lll)/m-CPBA systems. Some other processes promoted by mangancsc-salcn complexes can be found in [ 1.26, 32]. 

Figure 1. X-band EPR spectra (77 K) of 0.05 M solution of complex 1 in CHiCK (a) in CH2CI2 containing IM of NMO (b, c) spectrum of Mn"(saten) precursor of complex 2 in DMSO (d) spectrum of (salcn)Mn 0 complex recorded 1 min after reading complex I with one equivalent of/w-CPBA at 0 C(c) [49]. Spectrometer frequency 9.3 GHz, microwave power 40 mW, modulation frequency 100 kHz, modulation amplitude 20 G, gain 2.5xl0 (a-c), 1.0x10 (d), 2.5x10 (c).

Figure 7. H NMR spectra (CDCI CCIj 1 1, -78 °C ) befor rcauion (a) and at various moments of lime after addition of 1.2 cquiv. of w-CPBA 5 min (b). 15 min (c)...

Reagent i. pyridine ii. hv, MeOH iii. liAlH4 iv. AgOAc, I2, AcOH v. RuCls, NaI04 then CH2N2 vi. K2CO3, MeOH vii. TBDMSOTf, 2,6-lutidine viii. PhSeSiMes, Znl2 ix. w-CPBA ... 

Ring opening of (3-lactams at C2 C3 with application in peptide synthesis was first reported on a-keto (3-lactams 126 ([116] for applications of a-keto (3-lactams, see [117]), Scheme 42. These (3-lactams, readily available via oxidation of 3-hydroxy (3-lactams 125, undergoes a Baeyer-Villiger reaction upon exposure to w-CPBA and affords Wcarboxy a-amino acid anhydrides (NCAs) 127 [118]. Shortly after, it was discovered that a more direct, one pot route to these NCAs is feasible by treatment of 3-hydroxy (3-lactams with a solution of commercial bleach... 

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