Numbering spirocycles

Indeed, a number spirocyclic methodologies can be employed to prepare novel monomers for incorporation into libraries, and these have been reviewed extensively (Scheme 18.15). ... 

The reactions of the six-membered chlorocyclophosphazene were studied with a number of aliphatic diamines (169 175), aromatic diamines (176), aliphatic diols (177-179), aromatic diols (180,181) and compounds containing amino and hydroxyl functional groups (169,170,182). This subject has been reviewed (11,16,20). There are at least five different reaction products that are possible (Fig. 19). Replacement of two chlorine atoms from the same phosphorus atom produces a spirocyclic product. Replacement of two chlorine atoms from two different phosphorus atoms in the same molecule produces an ansa product. Reaction of only one end of the difunctional reagent, resulting in the substitution of only one chlorine atom, leads to an open-chain compound. Intermolecular bridged compounds are formed when the difunc-... 

Pseudorotation.—A number of spirocyclic phosphoranes possess square-pyramidal structures rather than the trigonal-bipyramidal structures previously assumed, and this could have important consequences on the interpretation of their variable-temperature spectra. There is, as yet, no evidence that acyclic or monocyclic phosphoranes favour the square-pyramidal geometry, and the variable-temperature XH... 

It has long been recognized that nitrone cycloadditions may allow access to spirocyclic ring systems. Such systems are inherently difficult to synthesize by conventional methods, yet are a structural component of a number of biologically active natural materials. Two common strategies have emerged for spirocycle generation from exocyclic or endocyclic nitrones (Scheme 1.45). In the exocyclic version, the carbon atom (arrowed) of the nitrone C=N double bond of dipole 209 carries a cyclic substitutent and thus an intermolecular cycloaddition reaction will... 

Holmes and his coworkers described a number of pentacoordinated anionic germanium complexes containing a spirocyclic framework with methyl, phenyl, halogen or hydroxyl ligand at the acyclic site307,332,333. Reaction of an organogermanium trichloride with a catechol or thiocatechol derivative in the presence of triethylamine, followed by a metathetical exchange, led to desired products as illustrated by the formation of the phenyl-substituted derivatives 90 and 91 (equation 16)333. 

Within the area of natural fibers, wool has the highest inherent nonflammability. It exhibits a relatively high LOI of about 25 vol % and low flame temperature of about 680°C.25 The inherent FR activity of the fiber can be associated with char-forming reactions which may be enhanced by a number of flame retardants. Based on their fundamental work to enhance char formation, Horrocks and Davies offer intumescent formulations based on MP to flame-retarded wool.61 From TGA and SEM characterization, they proposed a comprehensive model on the mechanism of protection via an intumescent process, which involves the formation of cross-linked char by P-N and P-0 bonds resistant to oxidation. More recently, they used spirocyclic pentaerythritol phosphoryl chloride (SPDPC) phosphorylated wool to achieve intumescent wool which exhibits large char expansion and good flame retardancy.62... 

Holmes and his coworkers described a number of pentacoordinated anionic germanium complexes containing a spirocyclic framework with methyl, phenyl, halogen or hydroxyl ligand at the acyclic Reaction of an organogermanium trichloride with... 

Unfortunately, experimental data on spirocyclic systems are insufficient so far and the number of examples is thus restricted (Table 1). 

Meyers used (2a) under a variety of conditions to ring close a number of enantiopure lactams to form spirocycles ranging in size from 5 to 8 members in 18 24h reaction times that conld then be converted to different targets in jnst a few steps (Table 6). ... 

A spirothietane sulfone-oxetane is a comonomer in the preparation of polyethers. A polymer obtained from this sulfone in a solution of bis(3,3-chloromethyl) oxetane with phosphorus pentafluoride can be spun to drawable filaments. Thietane sulfone spirocyclic carbonates may be polymerized via the carbonate group to high-molecular-weight solids said to be useful in laminating. Thietane 1,1-dioxide improves the dye receptivity of poly (acrylonitrile), viscose, cellulose acetate, and poly(vinyl chloride). It is also reported to be a stabilizer for nitric acid in oxidizer mixtures for rocket motors. 2-Methylthietane 1,1-dioxide is claimed to be superior to sulfolane (thiolane 1,1-dioxide) in the liquid extraction of aromatic hydrocarbons from mixtures with saturated hydrocarbons. " A number of bis(3,3-alkoxy) thietane 1,1-dioxides have been proposed as intermediates in the preparation of cyanine dyes useful as photographic sensitizers. " ... 

The spiroannulation approach described in Scheme 1 has been easily extended to analogous 1,2-dimethylenecycloalkanes. A wide variety of spirocycles have been synthesized from the reactions of magnesium complexes of 1,2-dimethylenecyclopentane and 1,2-dimethylenecycloheptane with l,n-dibromoalkanes and are shown in Table 1. Therefore, the present spiroannulation method provides a very general approach to a large number of spirocarbocycles with different combinations of ring sizes. 

Inorganic Chemistry of the Main-group Elements Evidence for five-co-ordinate phosphorus (v) species with essentially square-pyramidal structures has been observed in a number of spirocyclic systems, such as (79)470 and (80).471,472 Complete structural data are available... 

A number of new five-co-ordinate spiro-phosphoranes such as (102), obtained from P(NMe2)s and ephedrine," " and (103)" have also been synthesized. In compound (104), replacement of the dimethylamino-group with both mono- and di-hydroxy species has been studied,and i.r. investigations on a number of similar compounds, but containing P—H bonds point to the establishment of the equilibrium in equation (51) between the phosphorus(v) spirocyclic form and an... 

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