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

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Reaction Steps

(2,2-Difluoro-1-oxa-4,9-diazaspiro[5.5]undecan-4-yl)(2-isopropylthiazol-4-yl)methanone trifluoroacetate (example 44, step b) (0.40 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) (0.36 g) and AcOH (0.05 mL) in N-methyl-2-pyrrolidinone (5 mL). After 5 min, sodium triacetoxyborohydride (0.28 g) was added. After 16 h water was added and the mixture 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 20:80:5 ethyl acetate:isohexane:triethylamine separated the two isomeric products and gave the subtitled compound as a gum. Yield 0.24 g.

Provenance & Evidence