Spiro heterocycles

HETEROCYCLIC SPIRO COMPOUNDS Rule B-10. Compounds Method 1... 

Heterocyclic spiro compounds are named according to Rule A-42, the following criteria being applied where necessary (a) spiro atoms have numbers as low as consistent with the numbering of the individual component systems (b) heterocyclic components have priority over homocyclic components of the same size (c) priority of heterocyclic components is decided according to Rule B-3. Parentheses are used where necessary for clarity in complex expressions. 

Radicals derived from heterocyclic spiro compounds named by Rule B-10.1 are named according to the principles set forth in Rules A-11 and B-5.21. Radicals derived from other heterocyclic spiro compounds are named by adding -yl , -diyl , etc., to the name of the spiro compound (with elision of final e , if present, before a vowel). The numbering of the spiro compound is retained and the point or points of attachment are given numbers as low as is consistent with any fixed numbering of the heterocyclic spiro compound. 

Greenhill and coworkers have shown that the reaction of cyclic enaminones with isothiocyanates can be controlled regioselectively to attack the nitrogen or the / -carbon according to the reaction conditions8. Surprisingly, a heterocyclic spiro-product formed by reaction with two isothiocyanate molecules is observed in one case (equation 4). (equation 4). 

Several JV-(quinonylalkyl)enaminones have served as model compounds for an intramolecular Nenitzescu reaction demonstrating the ambident reactivity of both the enaminone and the quinone. The compounds cyclized unexpectedly, mainly to heterocyclic spiro-compounds146,147. A phenanthridinium salt and benzofuranoazocine are also obtained, depending on the length of the chain connecting the quinone and the enaminone moieties (equation 95). 

There are substances which do not belong to classes A-E, such as heterocyclic spiro oligomers. A few representative examples are mentioned here. 

Bemey, D. and Schuh, K., Heterocyclic spiro-naphthalenoncs. 1. Synthesi.s and reactions of... 

Under thermal conditions the heterocyclic spiro[2.4]heptene system undergoes rearrangement to a 5,6-dihydro-4-pyridone. This reaction is very useful when alkanenitrile oxides with appropriate leaving groups in the side chain are used because they lead to annulated dihydro-4-pyridones with a bridgehead nitrogen atom. - ... 

According to Huisgen (775, p. 36I) carbon disulfide adds to diphenyl-nitrilimine twice, i.e. successively to the two double bonds, with formation of a heterocyclic spiro compound (CXXXVIII). 

Keywords Microwave irradiation, green chemistry, organic synthesis, six and seven-membered heterocycles, spiro and fused heterocycles... 

The exocyclic C=S bond of 5-thioxo-2-thiazolines (203) can act as a dipolarophile towards several compounds. For instance, cycloaddition reactions have been reported with nitrilium betaines (204) to give heterocyclic spiro compounds <84HCA534>, with thiocarbonyl ylides (205) to give spirocyclic 1,3-dithiolanes <9IHCA1386>, and with 2-diazopropane (206) to give thiadiazoles <92HCA1825>. On the other hand, the reaction of (203) with diazomethane leads to a mixture of five products (Scheme 49) <93hcai715>. 

Similar palladium-catalyzed intramolecular dicarborations of dienes using aryl or vinyl halides and tributyl(vinyl)tin as reagents are known39,69. Thus, dienamide 2, containing the chiral pinene skeleton, gives the heterocyclic spiro adduct 3 with complete control of stereochemistry69. 

Spiro-linked compounds containing heterocyclic units have been prepared for many apphcations. In general, there are two synthetic pathways to build up heterocyclic spiro compounds. On the one hand, cross-coupling reactions like the Negishi, Kharash, Stille, Suzuki, or Sonogashira coupling reaction can be utilized to connect the heterocychc subunit with the central spiro core [118]. On the other hand, the heterocycle can be built up from spiro precursors containing heteroatoms. 

The heterocyclic spiro-oxindole moiety is found in a large number of alkaloids, which are important pharmaceutical compounds [44]. Several synthetic protocols are reported in the literature for the synthesis of these compounds [45]. Recently, Tao et al. [46] developed a direct asymmetric domino Michael/reduction/cychzation sequence for the construction of spiro[2H-pyran-3,4 -indohne] 99 from isatyhdene malononitrile 97 and acetone 98 in the presence of the chiral compound 100 (Scheme 9.20). 

When the reaction is conducted at 150 °C an oxazolo[2,3-c]pyrimidine is obtained . However, in the presence of a catalytic amount of boron trifluoride etherate, complex heterocyclic spiro compounds are produced (2 2 adducts). ... 

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