Isocal products

The INOC and ISOC processes, taken together, cover a wide range of substrates and generally give the target bicyclic products in yields from high to moderate. It should be noted that the reaction conditions for the INOC process are milder and the yields of bicyclic products are somewhat higher, while the ISOC process is substantially more selective. 

In the ISOC process alkenic silyl nitronates (649) are the reactive intermediates which undergo cycloaddition. This species is generated by reacting the nitroalkene (647) (Scheme 86) or nitroalkyne (651) (Scheme 87) with triethylamine and trimethylchlorosilane in benzene at room temperature for 48 h to give the fused isoxazole systems (648) or (652). A cis relationship between the less bulky C-7 and the hydrogen at C-3a in the products (648) is preferred. The yields of the reactions average... 

Hassner et aL reported an oxa-Michael addition of allyl alcohols 150 to nitroalkenes 75 followed by ISOC reaction (Scheme 40) [141]. The ISOC reaction conducted without isolating the intermediate nitroalkane 151 was superior to the stepwise mode in most cases in terms of its one-pot nature and product yield. 

While the diastereoselectivity was high when the INOC reaction of substrates possessing a chiral center at the allyhc position was conducted, the chiral center at the cr-position of the nitrile oxide moiety provided the isoxazoUnes 206 with moderate selectivity [153]. The ISOC provided better selectivity as compared to the INOC at the expense of the product yields. 

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