I want to know how much the Enlightenment philosophers knew of the works of Confucius. This page cites a translation from 1687 into Latin, while Wikipedia talks of 3 different translations before 1700, apparently all into Latin. I think it's safe to assume that any philosopher at this time could read Latin.
The first published translation was to Dutch in 1675
According to the very recent paper Dijkstra, T. & Weststeijn, T., (2017). Constructing Confucius in the Low Countries. De Zeventiende Eeuw. Cultuur in de Nederlanden in interdisciplinair perspectief. 32(2), pp.137–164. (Available online here), it was not a Latin translation that has been the first one published:
The first translation of Confucius’s Analects into a European language was a Dutch book by Pieter van Hoorn. Printed in Batavia in 1675, it predated the better-known Latin translation, Confucius Sinarum Philosophus (1687).
The first published and acknowledged translation
As mentioned by Mauro Allegranza, the first translation widely available in the west was Confucius Sinarum Philosophus, translated by Philippe Couplet, Prospero Intorcetta, Christian Wolfgang Herdtrich, François de Rougemont, and others, published in 1687. It is available with the original text and English translation (ISBN 9788870412062, published 2011) under the name Confucius Sinarum philosophus (1687) : the first translation of the Confucian classics. The title pretty much says it all.
One could say that these, in fact, are, for the most part, the first translations of Confucius despite the book by Pieter van Hoorn, as the above-mentioned paper points out:
According to Thierry Meynard’s recent overview, for Confucius Sinarum Philosophus ‘the Jesuits accumulated one hundred years of expertise in reading the Four Books and their commentaries’
(referring to: T. Meynard, The Jesuit reading of Confucius. The first complete translation of the Lunyu (1687) published in the West, Leiden 2015, p. 18.)
The truthfulness of early translations
Again referring to the Dutch paper, it obviously was not that much of Confucius in these translations:
Modern scholarship has debated whether the Jesuits in their translation effort may have ‘invented’ or ‘manufactured’ Confucianism.
And, later on:
The reviews printed in the Netherlands of Confucius Sinarum Philosophus recognized the Catholic slant the Jesuits gave to their translation
Philosophers reading early translations of Confucius
As of philosophers reading them, Leibniz comes to mind. David E. Mungello writes in his paper Leibniz's interpretation of Neo-Confuicianism (Philosophy East and West, Vol. 21, No. 1 (Jan., 1971), pp. 3-22):
From his early youth, Gottfried Wilhelm von Leibniz (1646-1716) developed an interest in China. In approximately 1666, at the age of twenty, he read G. Spizel's De Re Litteraria Sinensium Commentarius (Leiden, 1660), and soon afterwards, Fr. Athanasius Kircher's China Monumentis Illustrata (1667). He discovered Andreas Miller's attempt to construct a Key to Chinese in 1679. He apparently read Confucius Sinarumn Philosophus (1687) in the year of its publication. (emphasis mine)
The source for his last sentence here is "Joseph Needham, Science and Civilisation in China, 4 vols. (Cambridge: Cambride University Press, 1956), II, 497"
The great influence Confucius had in Leibniz' times is noted by Hegel in his lectures on the history of philosophy:
The first subject of remark with regard to the Chinese respects the teaching of Confucius (500 years before Christ) which made a great sensation in Leibniz's time; this teaching is a moral philosophy. Confucius has, besides, commented upon the old traditional principles of the Chinese; his high moral teaching, however, gave him his great fame, and that teaching is the authority most esteemed in China. (emphasis mine)
As ever so often, he is quite derogatory only a few sentences later, though:
Cicero gives us De Officiis, a book of moral teaching more comprehensive and better than all the books of Confucius. He is hence only a man who has a certain amount of practical and worldly wisdom — one with whom there is no speculative philosophy. We may conclude from his original works that for their reputation it would have been better had they never been translated. The treatise which the Jesuits produced is, however, more a paraphrase than a translation.
The last sentence implies that he actually read on Confucius himself in the early and at least one additional translation comparatively or a text whose author did that. Otherwise, it is hard to understand how he reached that conclusion.
In between the two of them, one of the more famous names mentioned is Wolff, the metaphysician that considered himself as heir of Leibniz and was the main position Kant argued against, as it used to be the state of the art metaphysics:
The German interest in Confucius in the early eighteenth century culminated in Christian Wolff’s famous defense of the Chinese as rational beings who had no need of the Christian god. (see also the Dutch paper)
But how influential was he?!
Well, this may, as always, be subject to discussions. But the Dutch researchers write:
Their [i.e. the Jesuits] edition, Confucius Sinarum Philosophus, appeared in Paris in 1687. This was a seminal historical moment on a global scale: as the Dutch sinologist Kristofer Schipper emphasizes, Confucius was the world’s ‘first philosopher to become famous outside his country, in other continents and civilizations’. Arguably the impact of this ‘most influential thinker in human history’ on the cultures of Asia is ‘as big as the combined influence of Socrates and Jesus on that of the West’.
They later draw lines from Confucius to Spinoza, which would, in fact, be mindblowing, as Spinoza could be considered one of the main drives of post-kantian philosophy in Germany, which resulted in the philosophies of Hegel and Marx.