What nouns can ながら turn into adverbs, and how does this differ from に? (残念ながら、当然ながら...)

Question

I learned 残念ながら quite early on and simply took it at face value, but as I've gained experience in Japanese I've come to question why this piece of grammar has two seemingly unrelated uses - expressing the simultaneity of two actions and turning certain nouns into an adverb.

I'm unsure which nouns beyond the one in the title this works with, if any. (Can I say 普通ながら?) Are they simply set phrases? Is this a different ながら from the other meaning? How does these constructions differ from, say, 当然に?

Answer 1

～ながら is sometimes translated as an adverb (e.g. 残念ながら = regrettably, unfortunately), but saying "ながら turns a noun into an adverb" is misleading. This ながら is close to while, although or despite. In English, while is particularly close to ながら in that it not only describes two actions happening simultaneously but it also expresses a contrast.

ながら can follow almost any noun, na-adjective and even i-adjective, but you should use it sparingly because it sounds fairly stiff or literary. Usually (だ)けど or (だ)が is preferred.

Examples:

• 残念ながら事実です。
  (literally: While that is regrettable, that is true.)
  Regrettably, that is true.
• 失礼ながら申し上げますと、…
  (literally: Although this is rude, I will say ...)
  I am afraid to say this, but ...
• 困難な仕事ながら、やる価値がある。
  While it's a difficult job, it's worth doing.
• 彼の成績は普通ながら、才能は突出している。
  Despite his unremarkable grades, he has an outstanding talent.
• 貧しいながら、末永く幸せに暮らしました。
  Although poor, they lived happily ever after.

How does these constructions differ from, say, 当然に?

～に modifies a verb, whereas ～ながら (sometimes) works like English "sentence adverbs". See this discussion.

Answer 2

ながら can be used in different ways although similar. While we just simply translate 残念ながら as unfortunately. It still literally means "while being unfortunate"

1. While doing A, also doing B V + ながら～（e.g. 歩きながらタバコを吸う。）
2. Even/Although/In spite of A, B. n/A + ながら～　(e.g 外国人ながら日本語をしゃべります。)
3. With/While being A, B n/A + ながら～　(e.g 残念ながら日本語試験に失敗した。)

I am not sure about which nouns beyond these samples are being commonly used with this form. Either way I hope this helps.