Bicycles spiro

At present, cyclic phosphoranes have been classified into four main families (Figure 4) monocyclic, bicyclic (spiro and fused), tricyclic and tetracyclic. 

Similar experimental results were observed recently in our laboratory (154). Indeed, the lithium enolate of bicyclic spiro ester 499 gave almost exclusively the equatorial product 500 (E= CgHjS, CH3S, CgHgSe, CH3 or 1) on reaction with various electrophiles. 

Other reviews and chapters of books which only discuss a specific heterocycle are mentioned in the appropriate section of this chapter. The organization of the chapter is similar to that adopted previously except that the (3-lactams have been divided into monocyclic 3-lactams (including bicyclic spiro compounds) and fused (3-lactams . The latter heading embraces a large volume of work and the reporting is necessarily more than usually. selective. 

The development of efficient methods to selectively control the formation of the Spiro center is therefore a topic of importance [1]. Among the various approaches employed for this purpose, metal-catalyzed construction of the bicyclic spiro moiety constitutes one of the most appealing strategies in terms of chiral economy and environmental considerations. Although molecules containing a spirocyclic framework are quite common in nature, the synthesis of the spiro backbone is not an easy task. This chapter deals with the recent advances in the preparation of spiro... 

Chang H-K, Datta S, Das A, Odedra A, Liu R-S (2007) PtCl2-Catalyzed hydrative cyclizatimi of trialkyne functionalities to form bicyclic spiro ketones. Angew Chem Int Ed Engl 46 4744 747... 

Das A, Chang H-K, Yang C-H, Liu R-S (2008) Platinum- and Gold-catalyzed hydrative carbocyclization of oxo diynes for one-pot synthesis of benzopyrenes and bicyclic spiro... 

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

For a related diastereoselective route to spiro-fused bicyclooctanes, see refs 144-147. The construction of bicyclic compounds with a cis ring junction is also used in the formation of key intermediates, such as 5, for forskolin148 149 and vernolepin150,151, see also ref 152. 

Recently, [2+3] cycloaddition reaction of 2-acetyl-[l,2,3]diazaphosphole (6) with 9-diazofluorenes (96) has been reported [105, 106], From the reaction in cyclohexane at rt, bicyclic phosphirane 97 was obtained as a result of the loss of nitrogen from the initial cycloadduct (Scheme 30). The cycloadduct, 3-spiro substituted 3H-[l,2,4]diazaphospholo-fused [l,2,3]diazaphosphole (98) could be isolated in good yield at room temperature in one case (R=/Bu) its stability was assigned to the presence of bulky fert-butyl group at 7-position. Use of polar solvent like dichloromethane led to the cyclic trimeric compound 99 (Scheme 30). 

Nair and co-workers reported the diastereoselective synthesis of spiro y-butyro-lactones from 1,2-dicarbonyls [125]. The authors studied the reaction with 1,2-cyclohexane dione 230 which produces the desired lactone 232 in good yields Eq. 22a. Isatins 233 are more reactive, but the products 235 are obtained as a 1 1 separable mixture of diastereomers Eq. 22b. The Nair research group extended this methodology to include homoenolate addition to tropanone 236 to form bicyclic 5-lactones 238 Eq. 22c [126]. 

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