NaBH4

NaBH4. See borohydrides. Prepared NaOMe plus B2H6. Used in organic reduc-... 

The synthetic equivalents of the synthon H" are the hydride donors sodium borohydride NaBH4, and lithium aluminium hydride LiAIHi. How might you make TM 21 using this disconnection ... 

Note that NaBH4 reduces aldehydes (and ketones) but not esters while L1A1H4 reduces just about all carbonyl compounds. Neither reagent reduces an isolated deuble bond. 

Anyway, there have been two very hot topics in chemistry lately clay microwaves. Both have been shown to do remarkable things in preparative organic chemistry. And this article Strike has [58], has combined both to produce some stunning reductive ami-nations of ketones to final amine products. The procedure involves mixing naked ketone, the amine, some clay and some NaBH4 in a beaker and zapping it in the microwave for only a couple of minutes. That s it. The general procedure is as follows ... 

A cousin to this reduction is one using stannous chloride (a.k.a. SnCb, a.k.a. Tin chloride) which is done exactly as the calcium one except that about lOOg of SnCb is used in place of the Mg or Ca and the addition occurs at room temperature and the solution is stirred for one hour rather than 15 minutes. Some very good reductions that operate almost exclusively at room temperature with no pressure and give almost 100% yields are to follow. The only reason Strike did not detail these methods is that some of the chemicals involved are a little less common than Strike is used to but all are available to the public. These alternatives include acetlylacetone and triethylamine [73], propanedithlol and trieth-ylamine [74], triphenylphosphine [75], NaBH4 with phase transfer catalyst [76], H2S and pyridine [77], and palladium hydrox-ide/carbon with hydrazine [78], stannous chloride dihydrate [85]. 

This catalyst has not been given a fair shake in underground literature and, as of this book s printing, is still relatively safe to purchase, A prudent chemist will most likely stock up on this chemical because the eventuality of more intense scrutiny is inevitable. The best way to make this product is to start with NaBH4 which is much more safe to buy. However, the way to go about making this catalyst is not very safe unless strict adherence to safety is used. 

Usually esters cannot be reduced directly to the corresponding ethers. Eflicient conversion with the NaBH4 —BF3 reagent is only possible, if the alcohol component is tertiary (G.R. Pettit, 1962 B). 

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