Applications of nitrile oxides

New applications of nitrile oxide 1,3-DC have been reported. Soluble, single-wall carbon nanotubes (SWNT) 32 functionalized with pentyl esters at the tips and pyridyl isoxazoline rings along the walls were prepared using pentyl ester-SWNT as dipolarophile. The complex... 

The chemistry of nitrile oxides is well documented. Several important monographs either specially devoted to nitrile oxides or including corresponding comprehensive chapters should be mentioned (1—5). Several reviews appeared (6—8), which concern preparation, reactivity, and synthetic applications of nitrile oxides. Some books and reviews devoted to individual aspects of nitrile oxide chemistry will be cited elsewhere. 

I.4.2.2. Cross-linldng of Polymers Among applications of nitrile oxides, cross-linking of polymers is of main importance. Both nucleophilic addition and 1,3-dipolar cycloaddition are the pertinent reactions. 

The many successful applications of nitrile oxide cycloadditions in synthesis are intimately linked with theory, both the simple FMO variety as well as the more sophisticated ab initio treatment, where the work of Sustmann and subsequently of Houk and his group has been seminal. We, the practitioners, have thus been supplied with a consistent view on the nature of 1,3-dipoles, their reactivity toward dipolarophiles, and the origin and interpretation of stereoselectivity of cycloaddition chemistry. It is of course desirable that our understanding of the relative reactivities of alkenes as well as of many 1,3-dipoles would be also improved, thereby leading to simple, extended recipes for the chemist practicing synthetics. We hope that this account will stimulate further advances in this field of cycloaddition chemistry and promote further uses of nitrile oxides in organic synthesis. 

S. Kanemasa u. O. Tsuge, Recent Advances in Synthetic Applications of Nitrile Oxide Cycloaddition (1981-1989), Heterocycles 30, 719 (1990). 

Kozikowski s group has been particularly active in the application of the INOC reaction toward the construction of a variety of natural products. One of the many examples from his laboratory involves the synthesis of tetracyclic compounds possessing suitably functionalized C rings for elaboration to a diverse number of ergot alkaloids via the INOC reaction. A total synthesis of chanoclavine I (65) was accomplished by this chemistry (Scheme 15). The key step in the synthesis involved the conversion of the nitro group of indole (62) into the corresponding nitrile oxide using the phenyl isocyanate procedure developed by Mukaiyama.57 The major product corresponded to isoxazoline (64). The isoxazoline nucleus was converted into chanoclavine I (65) in a series of subsequent steps. The application of nitrile oxide cycloaddition chemistry to the construction of other natural products can be expected to be an active area in future years. 

S. Kanemasa and O. Tsuge, Recent advances in synthetic applications of nitrile oxide cycloaddition (1981-1989), Heterocycles 1990, 30, 719-736. 

Kurth and co-workers prepared libraries of polyisoxazolines 39,40 by solid-phase combinatorial synthesis utilizing polymer-bound olefin 34, nitro-selenoethers 13c and nitroalkanes 13d,e (Scheme 11) [103]. An iterative application of nitrile oxide 1,3-dipolar cycloaddition followed by selenide oxida-tion/elimination steps was employed to afford polymer boimd tri-isoxazolines which could be liberated from the resin via trans-esterification to afford 39,40. 

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