Were there any "quasi-ecumenical" OO synods after 451? I mean something like the Synod of Jerusalem (1672) for the EO.
The first time the Oriental Orthodox Churches met together after 451 was in 1965 in Addis Ababa, Ethiopia. This Conference of the Oriental Orthodox Churches was summoned by His Imeperiel Majesty Haile Selassie I, the last Oriental Orthodox Emperor of Ethiopia. The Coference was attended by:
H.H Pope Kyrillos VI of Alexandria (Pope of Alexandria)
H.H Moran Mor Ignatious Yakub III (Patriarch of Antioch and all the East)
H.H Vazgen I (Armenian Catholicose)
H.H Khoren I (Armenian Catholicose of Cilicia)
H.H Moran Mor Baselious Augen I (Catholcose of the East; India)
H.H Abuna Baselios (Ethiopia)
Such a conference will be impossible now. This happened in 1965 before the seperation/schism between the Syriac Orthodox Church of Antioch and the the Indian Syriac Church.
H.I.M Haile Selassie I opened the conference and two of the heads, H.H Yakub III of Syriac Church and H.H Vasken of the Aremnian Church spoke immediately after the Emperor, thanking the Emperor. H.H Kyrillos was not present at the inauguration. He came in a day late.
The following is from the speech of H.H Ignatious Yakub III, Patriarch of Antioch at the conference.
To you Imperial Majesty and to the people of Ethiopia, especially to our brethren in the Ethiopian Orthodox Church, we and our Bishops bring the warmest regards of the Syrian Orthodox Church all over the world. We have with us in this conference our exalted Brother, Mar Baselios Augen I, the Catholicos of the East, leading a delegation of his ancient Church in India. It gives us great joy to see that in spite of his old age our beloved brother has journeyed from far-off India to Ethiopia to take part in this Conference. May we convey to Your Majesty, the church and people of Ethiopia the warmest greetings also of the Syrian Orthodox Church of India.