ISOXAZOLE ANNELATION REACTION

Hydrogenolysis of methylenediisoxazoles have been useful in preparing substituted resorcinols and aminophenols (7). The isoxazole annelation reaction (71,89,90,91,103) is well suited to the synthesis of steroids and other complex molecules. 

Isotetralin, 54, 11 ISOXAZOLE ANNELATION REACTION 1-METHYL-4,4a,5,6,7,8-HEXA-HYDRONAPHTHALEN-2 (3H) -ONE,... 

ISOXAZOLE ANNELATION REACTION l-METHYL-4,4a,S,6,7,8-HEX AHYD RONAPHTHALEN-2(3H)-ONE, 53, 70... 

The isoxazole annelation reaction - is a general method for fusing a new cyclohexanone ring onto an existing system and is complementary to the well-known Robinson annelation. It has several major advantages ... 

An isoxazole annelation reaction has been utilized to prepare (inter alia) dl-progesterone and d1-homotestosterone ... 

When recent advances in the chemistry of isoxazoles were reviewed by Kochetkov and Sokolov1 in this Series in 1963 (and by Quilico2 in 1962), the main features of isoxazole chemistry had been established. Since then some important new discoveries have been made, but probably the most significant advances have concerned the exploitation of the known features of their chemistry in synthesis. Particularly noteworthy developments include the further application of the cycloaddition of nitrile oxides in the synthesis of isoxazoles (Section II,C and D), the use of isoxazolium salts in peptide synthesis (Section III,B,2), syntheses involving the products of reductive cleavage of isoxazoles as intermediates (Section III,D and E) and annelation reactions via deprotonation of alkylisoxazoles (Section 1II,E). 

Sandmeyer synthesis (isatin) 145 Schmidt-Druey synthesis (pyridazine) 461 Schollkopf synthesis (oxazole) 173 Sharpless-Katsuki epoxidation 24 Shaw synthesis (pyrimidine) 468 Skraup-Doebner-Miller synthesis (quinoline) 400 Smiles rearrangement 446 Sommelet-Hauser rearrangement 136 Staudinger reaction 53 Steglich reagent (DMAP) 348 Stork isoxazole annelation 191... 

Isoxazole rings were annelated onto 5-nitroquinoline and isoquinoline-based o-nitrobenzyl-p-tolylsulfones by treatment with potassium phenoxide, which acted as both base and reductant (Equation (42)) <95H(40)187>. In the cases of quinolines as starting materials, product benzisoxazoles (75) both with and without phenoxy substitution were obtained, but in the case of an isoquinoline starting material no phenoxy-substituted product was generated. The reaction is thought to proceed via a nitrosobenzylsulfone carbanion intermediate, and can be applied to nitronaphthalenes but not to less active nitrobenzenes. 

---