Spiro compounds Boron trifluoride etherate

Spiro compounds Boron trifluoride etherate, 43 Potassium ferricyanide, 255 Triphenyltin hydride, 335 Sulfides... 

The spiro aziridine 202 (Scheme 3.74) reacts with a catalytic amount of boron trifluoride etherate to give rise to ring-expanded compound 205 in almost quantitative yield [55]. A possible mechanism involving intermediates 203 and 204 was proposed. 

Hydrolysis of the trifluoroacetyl-derivative (153) produces a mixture of the pyrrolin-2-ones (154) and (155) the latter is unstable, and gradually isomerizes to the former." Whereas the 7V-benzyl- and N-phenyl-pyrrolin-3-ones (156 R = CH2Ph or Ph) exist in the keto form shown, the iV-methyl derivative forms an equilibrium mixture of keto (156 R = Me) and enol tautomers (157)." The reaction of the pyrrolinone (158) with p-nitrobenzaldehyde unexpectedly yields compound (159)." The product of the action of thiobenzoic acid on (160) is the spiro-pyrrolinone (161), contrary to a previous report." Treatment of p-hydroxyphenylacetic acid with di-isopropylcarbodi-imide gives the imino-pyrrolinone (162), which rearranges to the bridged spiro-compound (163) in the presence of boron trifluoride etherate." ... 

It was reasoned, therefore, that if a bifunctional spiro ortho ester could be prepared and a small amount of this bifunctional material were to be copolymerized with the l,4,6-trioxaspiro[4.4] nonane (I), a lightly cross-linked elastomeric material could be produced with essentially no change in volume. Model compounds showed that phenyl glycidyl ether would condense with Y bwtyro-lactone to produce a substituted spiro ortho ester in a 50% yield and that this material would indeed polymerize at 30" in the presence of boron trifluoride etherate. 

When the reaction is conducted at 150 °C an oxazolo[2,3-c]pyrimidine is obtained . However, in the presence of a catalytic amount of boron trifluoride etherate, complex heterocyclic spiro compounds are produced (2 2 adducts). ... 

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