Mono spiroacetals strategy

Scheme 8 Kulinkovich coupling/ring-opening strategy toward mono(benzaimulated) spiroacetals...

Brimble and Haym have used dehydrative spirocycUzation to achieve the synthesis of a range of simple mono(benzaimulated) spiroacetals. The requisite dihydroxy-ketones were prepared via a Kulinkovich coupling/ring-opening strategy [52] (Scheme 8). Subsequent removal of the protecting groups under acidic conditions afforded the mono(benzannulated) spiroacetals 26 in moderate yield. 

Scheme 9 HWE/chemoselective reduction strategy toward mono(benzannulated) spiroacetals [53]...

Alternatively, the HDA approach toward mono(benzannulated) spiroacetals can make use of aliphatic dienes, rather than o-QM, as the 4n reaction partner. This strategy has been demonstrated most recently by Belmont et al. [163], where HDA between a variety of furoquinolines 313 and acrolein affords the spiroacetals 314 in good yield and selectivity (Scheme 77). 

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See also in sourсe #XX -- [ ]

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