Sodium triacetoxyborohydride → (9-((4-(2-(tert-Butyldimethylsilyloxy)ethyl)thiophen-2-yl)methyl)-1-oxa-4,9-diazaspiro[5.5]undecan-4-yl)(2-isopropylthiazol-4-yl)methanone

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Reaction Steps

(2-Isopropylthiazol-4-yl)(1-oxa-4,9-diazaspiro[5.5]undecan-4-yl)methanone trifluoroacetate (example 22, step b) (0.50 g) was added to a stirred solution of a 4:1 mixture of 4-(2-(tert-butyldimethylsilyloxy)ethyl)thiophene-2-carbaldehyde and 3-(2-(tert-butyldimethylsilyloxy)ethyl)thiophene-2-carbaldehyde (example 27, step b) (0.40 g) and AcOH (0.085 mL) in N-methyl-2-pyrrolidinone (6 mL). After 5 min, sodium triacetoxyborohydride (0.48 g) was added. After 16 h water was added and the mixture was extracted with ethyl acetate. The ethyl acetate layer was washed three times with water and evaporated in vacuo. Purification by silica gel chromatography eluting with ethyl acetate:isohexane:triethylamine, 20:80:5 separated the two isomeric products and gave the subtitled compound as a gum. Yield 0.27 g.

Provenance & Evidence