# Three stacked arrows, what does it signify?

I was checking the mechanism for the Lossen Rearrangement, when I came across the chemical reaction denoted as follows:

I couldn't find any resource where this notation was talked about.

What do the three arrows stacked as follows mean? A possible example where this is applied in literature would be appreciated.

• Multiple reactions (I came across this in some IChO papers, so not a canonical reference) – Aniruddha Deb Sep 17 '20 at 15:07
• It indicates there are several reactions in between with different reaction conditions before you achieve the final product. @Aniruddha Deb says it simply (I thought you know better Safdar! :-)). – Mathew Mahindaratne Sep 17 '20 at 15:29

There is an explicit answer in section 3. Other Horizontal Arrows of prof. Santiago Alvarez' published work [1, p. 594]:

[…]
Finally, multiple arrows (7) are used as an ellipsis for several intermediate steps in a chemical reaction.

### Reference

1. Alvarez, S. Chemistry: A Panoply of Arrows. Angew. Chem. Int. Ed. 2012, 51 (3), 590–600. DOI: 10.1002/anie.201101767.

It means that after multiple (unspecified) steps, the substrate on the left is transformed into the product on the right. It can be mechanistic steps or synthesis steps (to infer from the context).

Here is an example from the literature where the authors have added "steps" to make it perfectly clear. (Nicolaou, Kyriacos Costa, et al. "The Diels–Alder reaction in total synthesis." Angewandte Chemie International Edition 41.10 (2002): 1668-1698.)