Abstract from

Cantate Domino– Sing to the Lord
1441 by Eugenius IV – Pope Eugene IV:

“The most Holy Roman Church firmly believes, professes and preaches that none of those existing outside the Catholic Church, not only pagans, but also Jews and heretics and schismatics, can have a share in life eternal; but that they will go into the eternal fire which was prepared for the devil and his angels, unless before death they are joined with Her; and that so important is the unity of this ecclesiastical body that only those remaining within this unity can profit by the sacraments of the Church unto salvation, and they alone can receive an eternal recompense for their fasts, their almsgivings, their other works of Christian piety and the duties of a Christian soldier. No one, let his almsgiving be as great as it may, no one, even if he pour out his blood for the Name of Christ, can be saved, unless he remain within the bosom and the unity of the Catholic Church.”

Nota Bene, from the Code of Canon Law of 1917, also known as the Pio-Benedictine Code, of legal effect from 19 May 1918, abrogated by Pope John Paul II's Code of Canon Law of 1983 on 27 November 1983, Canon 731 § 2. Vetitum est Sacramenta Ecclesiae ministrare haereticis aut schismaticis, etiam bona fide errantibus eaque petentibus, nisi prius, erroribus reiectis, Ecclesiae reconciliati fuerint.

“It firmly believes, professes, and teaches that the matter pertaining to the law of the Old Testament, of the Mosaic law, which are divided into ceremonies, sacred rites, sacrifices, and sacraments, because they were established to signify something in the future, although they were suited to the divine worship at that time, after our Lord’s coming had been signified by them, ceased, and the sacraments of the New Testament began; and that whoever, even after the passion, placed hope in these matters of the law and submitted himself to them as necessary for salvation, as if faith in Christ could not save without them, sinned mortally. Yet it does not deny that after the passion of Christ up to the promulgation of the Gospel they could have been observed until they were believed to be in no way necessary for salvation; but after the promulgation of the Gospel it asserts that they cannot be observed without the loss of eternal salvation. All, therefore, who after that time observe circumcision and the Sabbath and the other requirements of the law, it declares alien to the Christian faith and not in the least fit to participate in eternal salvation, unless someday they recover from these errors.”

Abstracts from

Summo Iugiter Studio, 1832 Encyclical of Pope Gregory XVI

In fact this Encyclical Letter
from 1832 of of Pope Gregory XVI
is largely about
Outside the Church there is no Salvation –
Extra Ecclesiam Nulla Salus.
And note most well Pope Gregory's reference to
the Greek Orthodox Church, which might be understood
in this context as a reference to all the Orthodox Churches and possibly (not definitely) to the Oriental Orthodox Churches as well. Even if Pope Gregory's reference was only to Greek and other "Eastern" Catholics, it is telling. Did Pope Gregory XVI believe that the Orthodox were already in the same Church, the only true Church, along with the Catholics?

Finally some of these misguided people attempt to persuade themselves and others that men are not saved only in the Catholic religion, but that even heretics may attain eternal life.

...

You know how zealously Our predecessors taught that very article of faith which these dare to deny, namely the necessity of the Catholic faith and of unity for salvation. The words of that celebrated disciple of the apostles, martyred St. Ignatius, in his letter to the Philadelphians are relevant to this matter: "Be not deceived, my brother; if anyone follows a schismatic, he will not attain the inheritance of the kingdom of God." Moreover, St. Augustine and the other African bishops who met in the Council of Cirta in the year 412 explained the same thing at greater length: "Whoever has separated himself from the Catholic Church, no matter how laudably he lives, will not have eternal life, but has earned the anger of God because of this one crime: that he abandoned his union with Christ." Omitting other appropriate passages which are almost numberless in the writings of the Fathers, We shall praise St. Gregory the Great who expressly testifies that this indeed is the teaching of the Catholic Church. He says: "The holy universal Church teaches that it is not possible to worship God truly except in her and asserts that all who are outside of her will not be saved." Official acts of the Church proclaim the same dogma. Thus, in the decree on faith which Innocent III published with the synod of Lateran IV, these things are written: "There is one universal Church of all the faithful outside of which no one is saved." Finally the same dogma is also expressly mentioned in the profession of faith proposed by the Apostolic See, not only that which all Latin churches use, but also that which the Greek Orthodox Church uses and that which other Eastern Catholics use. [Emphasis Added.]