The easily accessible reagent 2‐cyanoethyl‐bis (diisopropylamino) phosphoramidite is shown to be suitable for the in‐situ, 1H‐tetrazole catalysed, preparation of d‐nucleoside‐3′‐phosphoramidites. The latter compounds could be applied successfully as building blocks in a solid‐phase DNA synthesis using an automated DNA synthesizer.