Hello,
try somethink like

location /folder1/ {
rewrite /folder1/(.*)$ /app/$1 break;
proxy_pass http://site2.ltd;
proxy_redirect off;
// this is only for loging on site2 to see the ip of the user and not
the ip of proxy server
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_max_temp_file_size 0;
}

Best Regards,
Basti

p.s i use this to proxy an wordpress site

On 14.10.2016 12:53, avk wrote:
> Hi! Can you help? How use proxy_pass (or other methods) for proxy
> subfolder-requests? Example: site1.ltd/folder1 -> proxy to site2.ltd/app
> Thx!
>
> Posted at Nginx Forum: https://forum.nginx.org/read.php?2,270269,270269#msg-270269
>
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