Spiro-O-heterocyclics

Spiro-O-heterocyclics. Trimethylenechlorohydrin added dropwise with stirring to ice-cooled ethylmagnesium bromide prepared from Mg and ethyl bromide in... 

Ethylmagnesium bromide magnesium Tetrahydrofuran ring from ketones and 1,3-chlorohydrins Spiro-O-heterocyclics... 

Spiro-O-heterocyclics 19, 214 Spirohydroxylactams, ring contraction 19, 800 Spirostanes... 

JHC1169 E. Ajello, O. Migliara, and V. Spiro, J. Heterocycl. Chem. 9, 1169... 

Substrates of substructure C (Figure 6.3) have been used to prepare O-heterocycles as well. A recent survey studies the microwave-accelerated generation of conformationally restricted spiro[cyclohexane-l,r-isobenzofuran] derivatives via 5-cro-cyclization of the corresponding cyclohexenyl o-iodobenzyl ethers (Scheme 6.24) [21,72]. The double-bond position in the hexacycles could be controlled by thoughtful choice of starting material and reactions conditions. This study also constitutes one of the rare examples of electron-rich alkenes used in Mizoroki-Heck reactions [21,72]. 

In the presence of a double bond at a suitable position, the CO insertion is followed by alkene insertion. In the intramolecular reaction of 552, different products, 553 and 554, are obtained by the use of diflerent catalytic spe-cies[408,409]. Pd(dba)2 in the absence of Ph,P affords 554. PdCl2(Ph3P)3 affords the spiro p-keto ester 553. The carbonylation of o-methallylbenzyl chloride (555) produced the benzoannulated enol lactone 556 by CO, alkene. and CO insertions. In addition, the cyclobutanone derivative 558 was obtained as a byproduct via the cycloaddition of the ketene intermediate 557[4I0]. Another type of intramolecular enone formation is used for the formation of the heterocyclic compounds 559[4l I]. The carbonylation of the I-iodo-1,4-diene 560 produces the cyclopentenone 561 by CO. alkene. and CO insertions[409,4l2]. 

Indolines, benzoxazole, and benzothiazole are possible as 2-methylene heterocycles. The number of known spirooxazine derivatives is much less than for the spiropyrans. This may be partly due to lack of many substituted o-nitrosonaphthols and partly due to lack of sufficient stability of spiro-oxazines. The structures of parent spirooxazines and the Xmax of their photomerocyanine forms are listed in Table 5. The Xmax of the colored forms of compounds 41-43 are not described in the literature. 

M. A. Gal bershtam, N. M. Przhiyalgovskaya, O. R. Khrolova, I. B. Lazarenko, G. K. Bobyleva, and N. N. Suvorov, Photochromic properties of some N-substituted 3,3-dimethyl-6 -nitro-indoline-2-Spiro-2 -2/7-chromenes, Chem. Heterocycl. Cpds., 1977, 1309-1313. 

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