There isn't a method for as() called "transactions"
showMethods("coerce")
Function: coerce (package methods)
from="ANY", to="array"
from="ANY", to="call"
from="ANY", to="character"
from="ANY", to="complex"
from="ANY", to="double"
from="ANY", to="environment"
from="ANY", to="expression"
from="ANY", to="function"
from="ANY", to="integer"
from="ANY", to="list"
from="ANY", to="logical"
from="ANY", to="matrix"
from="ANY", to="name"
from="ANY", to="NULL"
from="ANY", to="numeric"
from="ANY", to="S3"
from="ANY", to="S4"
from="ANY", to="ts"
from="ANY", to="vector"
from="character", to="IDate"
from="character", to="ITime"
from="character", to="signature"
from="character", to="SuperClassMethod"
from="color", to="HLS"
from="color", to="HSV"
from="color", to="LAB"
from="color", to="LUV"
from="color", to="polarLAB"
from="color", to="polarLUV"
from="color", to="RGB"
from="color", to="sRGB"
from="color", to="XYZ"
from="data.frame", to="data.table"
from="data.table", to="data.frame"
from="derivedDefaultMethod", to="function"
from="function", to="classGeneratorFunction"
from="function", to="OptionalFunction"
from="groupGenericFunction", to="genericFunction"
from="NULL", to="OptionalFunction"
from="NULL", to="optionalMethod"
from="oldClass", to="S3"