Compounds C-8 spiro

A. CH-Index of open-chain and mono- and C. Spiro-compounds. . . . 3505... 

The reaction of arylnitrile oxides with 1,1-diphenylallenes gave a mixture of 4-methylene-2-isoxazolines (Scheme 106) with major attack at the C(2)—C(3) double bond (74JCS(P2)l30l, 76CSC67, 76CSC71, 72JCS(P2)1914) and not a mixture of the 4- and 5-methylene compounds. 1-Phenoxyallene and benzonitrile oxide produced a mixture of positional isomers and a spiro compound (Scheme 107) (79JOC2796). 

Benzonitrile oxide reacted with 3-phenyl-4-benzylideneisoxazolinone to produce two isomeric spiro compounds (Scheme 153) (72MI41609,72MI41608). The reaction of benzonitrile oxide with ketene produced a spiro derivative (67MI41600) with allenes, bis(spiroisoxazo-lines) along with monoaddition products were formed (Scheme 154) (79JOC2796, 70CR(C)-(271)1468). 

At first, acid-catalyzed cyclization of Hofmann degradation products was undertaken however, the cyclization proceeded via the 5-exo-trigonal mode instead of the 6-endo-trigonal mode, resulting in no benzo[c]phenanthridine skeleton. Dyke and Brown (114-117) reinvestigated Perkin s results (118,119) and established the structure of the cyclized products 196 and 197 derived from the methine base 194 (Scheme 36). Onda et al. (120,121) obtained the five-membered spiro compounds 198 and 199 by treatment of 195 with dilute hydrochloric acid. 

Kano et al. (161,162) also investigated the Stevens rearrangement of tetrahydroprotoberberine metho salts 302 with dimsylsodium and obtained the spirobenzylisoquinolines 303 in high yield (Scheme 56). Similarly C-homoprotoberberine 304 gave the new spiro compound 305, whereas B-homoprotoberberine 306 afforded only the Hofmann degradation product 307. 

Regardless of the stereochemistry at C-14, both diasteroisomeric indenobenzazepines 176 and 177 afforded the same spiro compound 320. The stereochemistry at C-8 (or C-13) is retained, and the hydroxyl group newly... 

On the other hand, deprotonation of cycloadduct 76 with sodium hydride in acetonitrile at 0°C afforded cyclic sulfilimine 78, the so-called 1,2-azathiabenzene derivative, together with a spiro compound 79 (see Equation (21) and Table 11) <1999TL1505>. 

Benzo[c]furans (isobenzofurans) are reactive molecules usually employed as reactive dienes in the synthesis of more complex molecules. In the synthesis of spiro compounds related to fredericamycin A, Kumar generated the trimethylsiloxytrimethylsilylbenzo[c]furan 125 from phthalide via two consecutive deprotonations and silylations of the resulting anions. Diels-Alder reaction of the isobenzofuran as shown below with a spiroenedione leads to the formation of an endo-exo mixtures that can be smoothly converted to the dihydroxydione <00IJC(B)738>. 

Spiro stannyl complexes can be prepared116 from tetraalkynyltin compounds Sn(C=CR)4 (R = Me, Et, n-Pr, i -Pr, n-Bu) upon reaction with BEt3. This synthesis route involves a TT-coordinated diorganotin compound, 72, as an intermediate which, upon heating in toluene, gives the spiro compound 73. 

Selective nitrile oxide addition at the internal C(4)=Ca double bond, to give the spiro compound, is described for 4-vinylideneoxazolidin-2-one (228). 

Cyclic imidate esters, 2-ethoxypyrrolin-5-one and 2-ethoxy-1II -indol-3-one, undergo 1,3-dipolar cycloaddition reactions with nitrile oxides, the reaction site being at the pyrroline C=N bond (317). Rigid and sterically congested pyrroline spiro compounds 148 demonstrate complete diastereofacial selection in site and regiospecific cycloaddition reactions with nitrile oxides to give products 149 (318). 

In order to obtain asymmetric spiro compounds, there are two different possibilities. First, one can connect two different chromophores via a common spiro center. The thiophene compounds 39a and 39b are one example [84, 85]. Second, one can connect two equal but asymmetric chromophores. Based on this principle are Spiro-PBD (40), spiro-bridged bis(phenanthrolines) (41) [86], and the branched compounds Octol (42a) and Octo2 (42b) [87]. Because of their symmetry, these molecules are chiral. The glass transition temperatures of 40 and 42b are reported to be 163 and 236°C, respectively [88], Unfortunately, reports on the thermal properties of 39 and 41 are lacking. 

We have met diosgenin as an example of a natural spiro compound (see Box 3.17), and further examination of the structure shows the double bond as in cholesterol, a second five-membered ring c/s-fused onto the five-membered ring D, as well as the spiro fusion of a six-membered ring. Before this structure dismays you, take it slowly and logically. It should not be too difficult to end up with the stereodrawing shown here. 

CS180 Turner, C. E. and H. N. El Sohly. Iso-cannabispiran, a new spiro-compound isolated from a Panamanian variant of Cannabis sativa L. Abstr Joint Meeting American Society of Pharmacognosy and Society for Economic Botany Boston July 13-17 1981 14. 

A methanobridge is also formed when 1-hydroxymethylhexahelicene (93) is treated with an acid, but in this case the primary product (94) rearranges into the spiro compound (95). The same product is formed when (93) is heated in hexachloroethane at 200 °C for 30 min, either in the presence or absence of trifluoroacetic acid, but not in naphthalene as the solvent under the same conditions 163). 

Even in the absence of a functionalized methyl group at C(l) a product like (95) can be formed. On heating 1,3,14,16-tetramethylhexahelicene (96), neat or as a concentrated solution in naphthalene, above 180 °C two spiro compounds (99) and (100)... 

Diazopyrrole 196 with diethyl acetylenedicarboxylate gives the spiro compound 197. Rearrangement of 197 gives the pyrazolo[l,5-c]pyrimidine 198 (74LA1550). 

The same procedure can be used to convert 22 to the spiro compound 148 using diphenylenemercury at 300 °C. 

The temperature of decomposition depends also on steric factors The spiro compound 196 c with the five-membered dithiaphospha ring is much more stable than the spiro compound 196 d with the six-membered hetero ring. Only in the latter compound can a stable 1.2-dithia-cycloalkane be formed by radical cleavage Once again the preparative behaviour is in accord with the results of mass spectroscopy (p. 112). 

Similar treatment of 1.1-spiro compounds leads to different results depending upon the number of atoms in the iro ring. The fivemiembered compound 207 a yields the cyclic 2-oxyphosphinic acid ester 208 a (60%) and only 8% of the 4-hydroxyphosphinic acid ester 209a (R = H). Acetic acid ist not necessary for these transformations. 207b and c (R = D, CH3) react in a similar manner ... 

---