Ring compounds spiro substitution

Spiropyrans refers in general to a (substituted) 27/-pyran having a second ring system, usually (but not necessarily) heterocyclic, attached to the 2-carbon atom of the pyran in a spiro manner as shown in structure 1 i.e., a carbon atom is common to both rings. Compounds in which the second ring system is merely a saturated carbocycle such as cyclohexyl or adamantyl are better considered simply as 2,2-dialkylpyrans, and are discussed in Chapter 3. 

Cyclopropyl-substituted 1,3-dienes react in the normal fashion in the Diels-Alder reaction. Most of the dienes have been incorporated in cyclic structures with additional strain added to the cyclopropane ring. Compounds of this type that have been studied rather extensively, include derivatives of 3,4-dimethylenetricyclo[3.1.0.0 "]hexane, " bicyclo[4.1.0]hexa-2,4-diene, ""- - """ spiro[2.4]hepta-4,6-diene, - -" - "-" - " - ° - " -... 

A large number of polycyclic heterocycles containing two or more six-membered rings that share two or more carbon atoms are known. For the majority of these systems, only one of the six-membered rings contains the heteroatoms and the other rings are fused carbocyclic rings such as cyclohexane, benzene, naphthalene, and in rare examples, anthracene. Systems in which more than one of the six-membered rings contain heteroatoms are also briefly discussed these include spiro-cyclic compounds and substituted naphthalenes. 

The photocyclization of a series of suitably substituted enamides [e.g. (197)] has been used to create spiro-substituted isoquinolin-l-ones (198) a ring system present in a range of natural products. Although a great variety of products is available by this route, compounds lacking CHjPh do not cyclize. 

Nitro-substituted indolino spiroben2opyrans or indolino spironaphthopyrans are photochromic when dissolved in organic solvents or polymer matrices (27). Absorption of uv radiation results in the colorless spiro compound [1498-88-0], C22H2gN202, being transformed into the colored, ring-opened species. This colored species is often called a photomerocyanine because of its stmctural similarity to the merocyanine dyes (see Cyanine dyes). Removal of the ultraviolet light source results in thermal reversion to the spiro compound. 

Based on a known synthesis of spiro compounds with six-membered rings [63] we succeeded in the stepwise assembly of terminal substituted mono-[64] and dispiranes [65]. Hereby the cyclisation of the dibromide 35 with TOSMIC (Iter. 1) is the keystep of the reaction sequence as the initial ketone functional group (36) is recovered. Four subsequent reactions led to the spirodibromide 40 (Iter. 2). Final spirocyclisation afforded the dispirane 41, representing a precursor for new calamitic liquid crystals (Fig. 16) [66]. 

The conformations of spiro-compounds containing the oxane ring have been reported (Scheme 5) (81CJC1132). They exist only in conformation 9a at room temperature at lower temperature, no indication of a second conformer was found. The methyl-substituted derivatives 10a and similar tricyclic analogs occur in the same conformation 11a. 

In the benzyl-substituted spiro compound 30 (Scheme 18), the phenyl ring (due to a weak intramolecular interaction) was folded over the 1,3-dioxan-3,6-dione moiety (78M1263) the ABMNX spin system in the H NMR spectrum therefore was analyzed in detail (in CDCI3). 

Simple alkyl-substituted dihydro-1,4-thiazines are readily converted into the corresponding 5-monoxides atmospheric oxidation is sometimes sufficient, although side reactions may also occur. The cyclohexene derivative (99), for instance, affords not only the oxide (100) but also the spiro compound (101) probably generated by ring contraction of a hydroperoxide intermediate (Scheme 42) <73US(B)(8)34l>. 

Vinylpyridines add to TV-alkyl- or phenyl-substituted maleimides to give unexpected 1 2 and 1 3 adducts. From the reaction of 2-vinylpyridine 99 with N-alkylmaleimides the 1 2 addition products 154, which are tetra-hydroquinoline derivatives, could be isolated in the presence of polymerization inhibitors. Furthermore, 1 3 adducts 155 are formed, representing an unusual type of cycloaddition involving the pyridine ring. On the other hand, 4-vinylpyridine 156 combines with 3 moles of dienophilic N-alkylmaleimides in the presence of polymerization inhibitors to afford the spiro compounds 157 (73HCA440). 

A number of solid state structures of N-substituted morpholines show (cf. Table XX) the substituents prefer exclusively the equatorial position on the chair conformer of the saturated 6-membered ring, as in a number of 2,2-spiro compounds (02JMC11). 

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