Reactions of Silylated Aliphatic Nitro Compounds

Aliphatic nitro compounds 1035 with an a-hydrogen atom are readily O-silylated by N-trimethylsilyl-N,N -diphenylurea 23b to give a mixture of 1036 or 1037 [99]. This silylation works in particularly well if Ri and or R2 are activating nitro or car- 

The liberated trimethylsilanol 4, however, reacts with the trimethylsilyl nitronate 

1040 to give nitroethane and hexamethyldisiloxane 7 [110, 114]. On addition of hexamethyldisilazane (HMDS) 2 or BSA 22a the liberated trimethylsilanol 4 would probably be silylated in situ to hexamethyldisiloxane 7, resulting in higher yields of 1042. 

O-Trimethylsilyl nitronates 1036 have been used in fluoride-catalyzed aldol-type condensations with aldehydes and ketones to give a-trimethylsilyloxy-nitro com- 

The synthesis of O-trimethylsilyl nitronates [143 a], the many synthetic apphca-tions of O-trimethylsilyl nitronates ]143b, 158, 159], and the chemistry of conjugated nitrosoalkenes have been reviewed [109]. 

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TBDMSCl-Assisted Reactions. Nitro aldol (Henry) reactions have been reported to be promoted by TBDMSCl. To a THF solution of tetra-n-butylammonium fluoride is added sequentially equimolar amounts of the nitro compound, aldehyde, and EtsN, followed by an excess of TBDMSCl (eq 11). Substitution of TMSCl for TBDMSCl reduces the yield of nitro aldol product. The authors speculate that TBDMSCl is responsible for activation of the aldehyde while n-Bu4NF activates the nitro compound. In a related method, primary and secondary nitro alkanes were treated with LDA in THF followed by addition of TBDMSCl to give the corresponding silyl nitronates. The silyl nitronates reacted with a variety of aliphatic and aromatic aldehydes which gave vicinal nitro TBDMS aldol products. ... 

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