Spiro-compound

In Spiro compounds, a single atom is common to two rings. There are two kinds of nomenclature for these. Where there are no fused rings present, the carbons of both rings are counted in one series as in the bicyclic nomenclature, and the hydrocarbon name includes the carbons of both rings as in the following example. 

4-Oxospiro[2.6]nonane-l-carboxylic acid methyl ester 

When ring fusion is also present, the two ring systems that share the spiro atom are given in brackets with splicing locants as shown in the following example. 

This name denotes that there is one spiro atom and a total of eight atoms (from octane) in the structure. The numbers in square brackets, [3,4], show that there are three atoms linked to the spiro atom in one ring and four atoms linked to the spiro atom in the other ring. 

Numbering starts with a ring atom next to the spiro atom and proceeds first around the smaller ring, then through the spiro atom, and then around the second ring. Heteroatoms are denoted by replacement nomenclature. 

Numbering starts with a ring atom next to a terminal spiro atom and proceeds around this terminal ring so as to give the spiro atoms as low numbers as possible. Trispiro names, etc., are formed similarly. 

Organic Chemist s Desk Reference, Second Edition 

In an attempt to see how our former standard potential energy functions PEP300. and PEP400, those used most extensively in our calculations, would behave towards the type of strain encountered with 

The parameter sets were modified slightly, as described in detail in the paper. This was done partly to conform to our new forms of potential energy functions, see sections 9 1, 9 2 and 11.6.2, partly to take into account the special problems encountered with torsional angles in spiro compounds containing small rings. The parameter sets were checked on cyclohexane, cyclopentane, cyclobutane and cyclopropane with good results except for the vibrational spectrxim of cyclopropane and the structure of cyclobutane which came out planar as in some of its derivatives. 

This point illustrates one conclusion of the work, that our potential energy functions are too primitive to account for large deviations from ideal geometry. Another conclusion was that our potential energy functions, despite their simple form and few parameters, are good enough for a first estimate of structure and thermodynamic functions even of these compounds. 

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The synthesis of spiro compounds from ketones and methoxyethynyl propenyl ketone exemplifies some regioselectivities of the Michael addition. The electrophilic triple bond is attacked first, next comes the 1-propenyl group. The conjugated keto group is usually least reactive. The ethynyl starting material has been obtained from the addition of the methoxyethynyl anion to the carbonyl group of crotonaldehyde (G. Stork, 1962 B, 1964A). 

A interesting and useful reaetion is the intramolecular polycyclization reaction of polyalkenes by tandem or domino insertions of alkenes to give polycyclic compounds[l 38]. In the tandem cyclization. an intermediate in many cases is a neopentylpalladium formed by the insertion of 1,1-disubstituted alkenes, which has no possibility of /3-elimination. The key step in the total synthesis of scopadulcic acid is the Pd-catalyzed construction of the tricyclic system 202 containing the bicyclo[3.2. Ijoctane substructure. The single tricyclic product 202 was obtained in 82% yield from 201 [20,164). The benzyl chloride 203 undergoes oxidative addition and alkene insertion. Formation of the spiro compound 204 by the intramolecular double insertion of alkenes is an exam-ple[165]. 

The first several perfluoro spiro compounds have also been synthesized (62). An example of this technology is the synthesis and crystal stmcture of perfluoro-1,4,9,12-tetraoxadispiro [4.2.4.2]tetradecane. 

Volatiles or Aroma. The essential oil, or aroma, of tea provides much of the pleasing flavor and scent of green and black tea beverages. Despite this, volatile components comprise only - 1% of the total mass of the tea leaves and tea infusions. Black tea aroma contains over 300 characterizing compounds, the most important of which are terpenes, terpene alcohols, lactones, ketones, esters, and spiro compounds (30). The mechanisms for the formation of these important tea compounds are not fully understood. The respective chemistries of the aroma constituents of tea have been reviewed... 

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. 

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). 

The acetoxy dienone (218) gives phenol (220). Here, an alternative primary photoreaction competes effectively with the dienone 1,5-bonding expulsion of the lOjS-acetoxy substituent and hydrogen uptake from the solvent (dioxane). In the case of the hydroxy analog (219) the two paths are balanced and products from both processes, phenol (220) and diketone (222), are isolated. In the formation of the spiro compound (222) rupture of the 1,10-bond in the dipolar intermediate (221) predominates over the normal electron transmission in aprotic solvents from the enolate moiety via the three-membered ring to the electron-deficient carbon. While in protic solvents and in 10-methyl compounds this process is inhibited by the protonation of the enolate system in the dipolar intermediate [cf. (202), (203)], proton elimination from the tertiary hydroxy group in (221) could reverse the efficiencies of the two oxygens as electron sources. 

Interestingly the Skraup/Doebner-von Miller reaction has been used to prepare a number of spiro-compounds. Aniline was reacted with enone 42 in the presence of iodine to yield dihydroquinoline 43 in acceptable yields. 

Spiro compounds containing adamantane and heterocyclic fragments 97KGS435. 

The Spiro compound 164 has been claimed as a product from the dimerization of the 2-substituted indole 165 after treatment with hydrogen bromide in acetic acid (69GEP1901637). A recent reinvestigation of this reaction, however, indicates that the cycloheptadundole 166 is in fact produced (98MI1), which is not unexpected, as similar dimerizations have previously been observed (89T5549). 

Similar cyclization of 367 leading to low yields (20%) of benzodithiine 368 was observed with triethylamine in DMSO (Eq. 32) (76ZOR844). On the other hand, coumarin derivative 369 treated with 1,2-ethanedithiole in the presence of triethylamine provided relatively stable spiro compound 370 (Eq. 33) (89ZOR669). 

Also. 77/-pyrrolo[l,2-fl]azepin-7-ones, e.g. 22, available by the thermal rearrangement of 1-azaspiro[4.5]dcca-l,3,6,9-tetraen-8-ones 21, in trifluoroacetic acid form the deep-blue 7-hy-droxypyrrolo[l,2-tf]azepinium cations, e.g. 23.219 In hot 48 % hydrobromic acid, however, the spiro compound 21 is re-formed. 

Heating ll-methyldibenz[6,/][l,4]oxazepine (3) with dimethyl sulfate in boiling toluene for two hours gives the methylene compound 4, which condenses with l-nitroso-2-naphthol to yield the thermo- and photochromic spiro compound 5.45... 

In a formal synthesis of fasicularin, the critical spirocyclic ketone intermediate 183 was obtained by use of the rearrangement reaction of the silyloxy epoxide 182, derived from the unsaturated alcohol 180. Alkene 180 was epoxidized with DMDO to produce epoxy alcohol 181 as a single diastereoisomer, which was transformed into the trimethyl silyl ether derivative 182. Treatment of 182 with HCU resulted in smooth ring-expansion to produce spiro compound 183, which was subsequently elaborated to the desired natural product (Scheme 8.46) [88]. 

Okada, M. Ring-Opening Polymerization of Bicyclic and Spiro Compounds. Vol. 102, pp. 1-46. 

Formation of the six-membered ring on cyclization of the ( )- and (Z)-4-nonenylhydroxylac-tams [E)-4 and (Z)-4 in formic acid, occurs completely stereoselectivcly to afford the 6.6-spiro compounds (7R )-5 and (7S )-5, respectively51,52. The reaction supposedly proceeds via a chair-like transition state, as depicted. Depending on the reaction conditions, however, 0.5 % 2 or about 25%51 of the five-membered ring isomers are also formed. 

However, exo-selective Diels-Alder reactions are found when a,/J-unsatu-rated exocyclic carbene complexes are used as dienophiles. The fixed s-cis conformation of the vinylcarbene moiety of the complex seems to be responsible for the exo selectivity observed in this reaction. Moreover, the reaction of optically active carbene complexes with 2-morpholino- 1,3-butadienes allows the asymmetric synthesis of spiro compounds [99] (Scheme 53). 

A second mole gives spiropentanes. In fact, any size ring with an exocyclic double bond can be converted by a carbene to a spiro compound. ... 

For a review of the preparation of spiro compounds by this reaction, see Krapcho, A.P Synthesis, 1978, 77. 

The 1,3,4-oxadiazole 113 is formed from the azo compound 112 by the action of triphenylphosphine <96SL652>. A general synthesis of 1,3.4-oxadiazolines consists in boiling an acylhydrazone with an acid anhydride (e.g., Scheme 18) <95JHC1647>. 2-Alkoxy-2-amino-l,3,4-oxadiazolines are sources of alkoxy(amino)carbenes the spiro compound 114, for instance, decomposes in boiling benzene to nitrogen, acetone and the carbene 115, which was trapped as the phenyl ether 116 in the presence of phenol <96JA4214>. 

The spiro compound 206 was prepared in five steps from (S)-l-naphthyl-ethylamine and was composed of a mixture of imine and enamine tautomers. Reduction of the imine function by sodium borohydride occurred on the less hindered si face, leading to the diamine with the R configuration of the newly formed stereo center, then the N-benzyl substituent was removed by hydrogenolysis to give 207 with good overall yield [98] (Scheme 30). 

Spiro compound (18), also containing two fIve-membered rings, can be made by oxidation of the acyloin (19) (Chapter T24). 

Schroder, H. Netscher, T. Determination of the absolute stereochemistry of vitamin E derived oxa-spiro compounds by NMR spectroscopy. Magrt. Resort. Chem. 2001, 39, 701-708. 

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