The phrase "as thereupon" is correct and can be used in written English.
It is typically used to indicate that something happens immediately after a particular event or action.
Example: "He made his decision, and as thereupon, he informed the team of the changes."
Alternatives: "thereafter" or "subsequently".
Alecky Blythe, a specialist in the thriving narrative form known as "verbatim theater," thereupon set about to interview the inhabitants of the specific street, London Road, on which the killer lived.
So eventually every patron who wound their way through the actual corral at the entrance and up to the register found himself or herself ordering the buffet, thereupon to feed for as long as possible at this ever-expanding golden trough.
In 1886 Parnell and Chamberlain arranged O'Shea's election to Parliament from Galway as a Home Ruler, but O'Shea (as Chamberlain evidently expected) thereupon refused to support a Home Rule Bill sponsored by the prime minister, William Ewart Gladstone.
Q e is thereupon derived as We measured μ v, δ) in the tRNAphe folding as shown in Fig. 7ab.
Next phase of concept phase is the release of design, thereupon the design is frozen, as well as the product bill of materials.
However, as a study that produces insight into both surface strata of attachment as well as methods of study thereupon, it is though it retains its import whether years old or not.
Leonard Calvert was thereupon deputized as governor of the colony, and in November 1633 he sailed from England in the ships Ark and Dove with 17 gentlemen and their wives and about 200 others.
Subsequently, he/she whitewashes himself/herself by creating a new account and thereupon behaving as an honest rater.
Attila thereupon claimed Honoria as his wife and demanded half the Western Empire as her dowry.
Julian's army thereupon hailed him as Augustus.
