Synthesis of lithium aminoborohydrides and reactions thereof

• US 5,466,798 A
• Filed: 10/15/1993
• Issued: 11/14/1995
• Est. Priority Date: 03/06/1992
• Status: Expired due to Fees

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Harrison, John, Fuller, Joseph C., Fisher, Gary B., Singaram, Bakthan, Goralski, Christian T.
• Primary Examiner(s): Kumar, Shailendra
• Application Number:
  US08/138,612
• Time in Patent Office: 760 Days
• Field of Search: 564/9, 423/179.5, 423/194, 540/541, 546/13, 548/405, 556/7, 556/8
• US Class Current: 540/541
• CPC Class Codes: C07C 213/00 Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton
• CPC Class Codes: C07C 215/08 with only one hydroxy group and one amino group bound to the carbon skeleton
• CPC Class Codes: C07D 295/084 with the ring nitrogen atoms and the oxygen or sulfur atoms attached to the same carbon chain, which is not interrupted by carbocyclic rings
• CPC Class Codes: C07D 295/088 to an acyclic saturated chain
• CPC Class Codes: C07D 295/092 with aromatic radicals attached to the chain
• CPC Class Codes: C07D 295/096 with the ring nitrogen atoms and the oxygen or sulfur atoms separated by carbocyclic rings or by carbon chains interrupted by carbocyclic rings

Abstract

The present invention relates to novel, powerful reducing agents, lithium aminoborohydrides which are prepared by addition of BH₃ •THF to the corresponding dialkylamine at 25° C. to give the intermediate amineborane complex. Subsequent deprotonation by strong base, e.g. n-BuLi, yields the aminoborohydride quantitatively. Lithium aminoborohydrides are powerful reducing agents, comparable in strength to lithium aluminum hydride. The activity is determined by the dialkylamine. Lithium pyrrolidinoborohydride has unique activity and selectivity in its reducing properties. Esters, lactones and anhydrides are reduced cleanly at 25° C. to give the corresponding alcohols, while carboxylic acids are not reduced. Test reductions show that lithium pyrrolidinoborohydride is also capable of reducing a wide range of functional groups including amides, epoxides, oximes, nitriles and halides.

Claims

1. A substantially pure lithium aminoborohydride having a purity of about 92% or higher purity of the structure:

space="preserve" listing-type="equation">Li.sup.+- BH.sub.3 NR.sup.1 R.sup.2

wherein

R¹ and R² are each moleties selected from;

alkyl having from 2 to 20 carbon atoms;

aryl having from 6 to 20 carbon atoms; and

R¹ and R² together form a cyclic ring having 4, 5, or 6 carbon atoms producing a lithium aminoborohydride selected from the group consisting of ##STR41##

2. The lithium aminoborohydride of claim 1 which is selected from:

##STR42##

3. The lithium aminoborohydride of claim 1 wherein R¹ and R² are both achiral.

4. The lithium aminoborohydride of claim 1 wherein R¹ and R² are each octyl.

5. The lithium aminoborohydride of claim 2 selected from:

##STR43##

6. The lithium aminoborohydride of claim 2 selected as:

##STR44##

7. The lithium aminoborohydride of claim 1 having the structure:

##STR45##

8. The lithium aminoborohydride of claim 1 having the structure:

##STR46##

9. The lithium aminoborohydride of claim 1 having the structure:

##STR47##

10. The lithium aminoborohydride of claim 1 having the structure:

##STR48##

11. The lithium aminoborohydride of claim 1 having the structure:

##STR49##

12. The lithium aminoborohydride of claim 2 having the structure:

##STR50##