Spirocyclic compounds => cyclic

An enantioselective variant of the diene cydization reaction has been developed by application of chiral zirconocene derivatives, such as Brintzinger s catalyst (12) [10]. Mori and co-workers demonstrated that substituted dial-lylbenzylamine 25 could be cyclized to pyrrolidines 26 and 27 in a 2 1 ratio using chiral complex 12 in up to 79% yield with up to 95% ee (Eq. 4) [ 17,18]. This reaction was similarly applied to 2-substituted 1,6-dienes, which provided the analogous cyclopentane derivatives in up to 99% ee with similar diastereoselectivities [19]. When cyclic, internal olefins were used, spirocyclic compounds were isolated. The enantioselection in these reactions is thought to derive from either the ate or the transmetallation step. The stereoselectivity of this reaction has been extended to the selective reaction of enantiotopic olefin compounds to form bicyclic products such as 28, in 24% yield and 59% ee after deprotection (Eq. 5) [20]. 

The reaction of cyclic esters with quinones give either symmetrical or unsymmetrical spirocyclic compounds. For example, symmetrical spirocyclic compounds have been synthesized as follows (192) ... 

There are many cyclic compounds known containing P and Si atoms in the ring but the majority have organic substituents on the silicon. (Details of the structures of such compounds are available.An exception is the spirocyclic compound (19), formed using an alkali metal-phosphorus derivative (equation 34). ... 

Acetamides of cyclic enaminones cyclized upon treatment with tributylstannane and AIBN to give spirocyclic compounds (equation 141). 

Tetrakis(dimethylamino)titanium ctmverts DMF to tris(dimethylamino)methane (529 equation 236)7- - - This compound is also formed in the reaction of A 7VJV, lV -tetramethyloxamide with the titanium reagent, whereas amides which have a-CH bonds are converted to ketene aminals7- Cyclic and spirocyclic compounds, ccmtaining the substitution pattern of a trisamino compound, are form in die reaction of IVJV-dialkylfonnamides or M-aiyl-N,/V- aIkylformamidines with aiyl isocyanates. Similar compounds, e.g. (530 equation 237), are produced in die reaction of imidazolines or lactamid-ines with isocyanates. 

Cycloadditions have emerged as one of the most used approaches for the formation of cyclic compounds by organocatalysis [8a]. Based on the previous knowledge, [3-1-2] cycloadditions can serve as an excellent platform for the synthesis of spirocyclic compounds. For example, alkylideneindolones act as activated alkenes that react with azomethine ylides to afford pyrrolidine derivatives. Recently, several research groups have used this approach to synthesize spirooxindoles and related... 

Ma and coworkers reported a similar reaction for the synthesis of spiro-3,4-dihydropyranes [44]. The reaction between cyclic p-oxo aldehydes and aromatic p,Y-unsaturated a-ketoesters catalyzed by the cinchona alkaloid derivatives afforded the corresponding spirocyclic compounds in good yields and moderate to good enantioselectivities. 

Intramolecular reactions of electron donor and acceptor sites in cyclic starting materials produce spirocyclic, fused, or bridged polycyclic compounds. 

Pavan Kumar et al. <2006NJC717> investigated the reaction of diethyl azodicarboxylate (DEAD) or diisopropyl azodicarboxylate (DIAD) with cyclic phosphates or phosphoramides in order to determine the structural preferences in spirocyclic penta- and hexacoordinate aminophosphoranes. They found that sulfur would coordinate to phosphorus to form the [3.3.0] bicyclic compounds 94-96. 

The synthesis of spirocyclic and fused unusual (3-lactam derivatives has been discussed. The 2-azetidinone skeleton has been extensively used as a template on which to build the carbo(hetero)cyclic structure joined to the four-membered ring, using the chirality and functionalization of the (3-lactam ring as a stereocontrolling element. In many cases the compounds described in this chapter were included because of an interesting synthesis or structure, although limited biological data were found. 

The first structural report of an alumo-poly siloxane appeared as early as 1966 the molecule (Me2SiO)4(OAlBr2)2(AlBr) has an Si4Al2Ofi 12-membered cycle which is spirocyclically bridged by an Al-Br unit (see Fig. 3).68 Only in 2000 was the corresponding structure of the chloro-derivative (which is iso-typic to the bromo-compond) published.69 In both compounds, all silicon and aluminum atoms are tetra-coordinate with the exception of the spiro-cyclic central bromo(chloro)-aluminum -moiety, which is penta-coordinate with four oxygen bonds. 

Cyclic nitrones 74a and 74b, when irradiated by 350 nm rays in acetonitrile at room temperature for 52 h, gave spirocyclic l,2-oxazetidin-3-ones 30a and 30b (85-90% yield) (Scheme 20). A mechanism for the formation of such compounds,... 

Methylenecyclopropane derivatives have been used as radical traps in radical cyclizations. This approach involves the 5-exo cyclization of a (methylenecyclo-propyl) propyl radical 33, followed by the opening of the resulting cyclopylmethyl radical 34 to give cyclohexyl radical 35 [55]. Radical cyclizations of methylenecyclopropane derivatives give a variety of cyclic compounds including spirocyclic and tricyclic compounds (Scheme 23). 

Chloranil oxidized a variety of methylarsenic(iii) esters, amides, or cyclic thioesters, products such as (89), for example, being obtained from a dithioester of methylarsonous acid. ° The analogous reaction with 2-iodo-l,3,2-dihetero-arsolans, however, proceeded with simultaneous cleavage of the As—I bond and formation of the spirocyclic arsenic(v) compound (90). The six-co-ordinate arsenic(v) anions (91) were produced by addition of an alcohol or phenol to an arsolan in the presence of triethylamine, the latter abstracting a proton and forming the required cation. ... 

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