Mesityl nitrile oxide

The only known representative of this type of compound, 91, was prepared by 1,3-dipolar addition of mesityl nitrile oxide to telluroketone 85 (93JA7019 94MI1). The reaction proceeds smoothly on heating equimolar amounts of the reactants at 80°C, giving rise to 91 in 70% yield. The heterocycle is a thermally unstable and light-sensitive compound. Thermolysis of a deuterochloroform solution of 91 at 60-90°C in a sealed ampule affords 1,1,3,3-tetramethylindanone and mesityl isonitrile (94MI1). 

The addition of mesityl nitrile oxide to stable derivatives of a germanethi-one21 and a germaneselone22 is closely related to the addition of nitrones. The reaction is regioselective again, with formation of the germanium-oxygen bond. 

A stannanethione and stannaneselone were found to give [2 + 3] cycloadducts with mesityl nitrile oxide.9... 

The 3 + 2-cycloaddition of nitrile oxides to 2-crotyl-l,3-dithiane 1-oxides produces exclusively 5-acyldihydroisoxazoles.92 Lewis acid addition to 1,3-dipole cycloaddition reactions of mesityl nitrile oxide with a, /i-unsaturated 2-acyl-1,3-dithiane 1-oxides can reverse the sense of induced stereoselectivity.93 The 1,3-dipolar cycloaddition of 4-t-butylbenzonitrile oxide with 6A-acrylainido-6A-deoxy-/i-cyclodextrin (68) in aqueous solution favours the formation of the 4-substituted isoxazoline (69) rather than the 5-substituted regioisomer (Scheme 24).94 Tandem intramolecular cycloadditions of silyl nitronate, synthons of nitrile oxides, yield functionalized hydrofurans.95... 

Phosphorus-containing heterocycles were also generated by the use of 7. Reaction of 7a or Me3SiP=C(OSiMe3)Ad (7b Ad = 1-adamantyl) with mesityl nitrile oxide gave the corresponding 1,2,4-oxaazaphosphole via [3 + 2] cycloaddition reaction, followed by elimination reaction (equation 56)74,75. 

A very elegant reaction is the synthesis by means of a 1,3-dipolarophilic cycloaddition of nitrile oxides with alkynylsilanes (equation 131)157. If mesityl nitrile oxide (288c) and... 

C (10 mmHg). In CeD, the PNMR shift was <5 +159, entirely consistent with the presence of a C=P double bond, and this was confirmed by the C NMR spectrum, which showed phosphorus to be directly coupled to an sp carbon (<5 194.7, Jfc 68.7 Hz) and to an sp carbon 37.1, /pc 51.4 Hz). The 27f-phospholes where the 2-phenyl was replaced by 2,4,6-trimethylphenyl, 2,4,6-trimethoxyphenyl, and methyl were also made in good yield by this method. These 2 -phospholes are thermally stable but very sensitive to water and were hydrated on attempted chromatography on Kieselgel to form the phospholanone (204). Other reactions observed (Scheme 46) included a Diels-Alder cycloaddition with methyl propiolate (giving (205)), and a 1,3-dipolar cycloaddition with mesityl nitrile oxide that formed (206). 

Sibi et al. reported that substoichiometric chiral Mg(II) complexes catalyzed regio- and enantioselective nitrile oxide cycloadditions to electron-deficient alkenes (Scheme 4.8) [6]. For an achiral template, bulky pyrazolidinone (20) was essential for high regio- and enantioselectivity in (22) and (23), while oxazolidinone crotonate and 3,5-dimethylpyrazole gave the adducts, but with poor results. In particular, mesityl nitrile oxide (21), a stable dipole, was chosen as the reagent due to steric interactions of that group with either a bulky achiral template and/or a bulky Lewis acid center. Aliphatic (t-Bu and i-Bu) nitrile oxides also provided cycloaddition... 

TABLE 7.10 Evaluation of Templates in Mesityl Nitrile Oxide Cycloadditions"... 

Asymmetric cycloadditions of mesityl nitrile oxide wifli 2-methyl-2-butenoyl type of imide dipolarophiles have also been investigated by use of similar lNDABOX-metal(ll) complexes (30mol%) (Table 7.12) [32]. As shown in... 

TABLE 7.12 Asymmetric Cydoadditions of Mesityl Nitrile Oxide with 2-Methyl-2-butenoyl Type of Imide Dipolarophiles Catalyzed hy INDABOX-MetalfD) Complexes... 

Asymmetric Cycloadditions of Mesityl Nitrile Oxide with Crotonoic Acid Derivatives Catalyzed hy (R)-BINIM-Ni(II)... 

Reactions were carried out by stirring mesityl nitrile oxide at rt in CH2CI2 in the presence of (/ )-BINIM-Ni(II) complexes. Catalyst loading of (/ )-BINIM-Ni(II) complexes. 

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