In short

This is the vocabulary of notices, job ads, contracts and formal email: 〜に際して (on the occasion of), 〜にわたって (spanning), 〜を通じて (throughout / via), 〜次第 (as soon as / depends on) and 〜を問わず (regardless of). Most bolt onto a bare noun, exactly like the compound particles of lesson 55 - 次第 is the exception, because its “as soon as” sense wants a ます-stem instead. Two things decide whether you get them right: which particle the item takes (に or を), and the single kana that separates にかかわらず (regardless) from にもかかわらず (despite).

The rule

Step 1 - Occasion and juncture: 〜に際して, 〜にあたって, 〜に先立って. These three mark the moment of a significant event - an opening, a departure, a launch, a contract signing. They are ceremonial: you use them about a graduation, never about eating lunch. All three take a bare noun or a dictionary-form verb:

Noun + に際して / V-dictionary + に際して.

• 〜に際して (ni saishite, stiffer variant 〜に際し) - “at the time of, on the occasion of”. Points at the event itself: 契約に際して身分証が必要です (Keiyaku ni saishite mibunshō ga hitsuyō desu, an ID is required when signing the contract). Adnominal: に際しての (ご利用に際しての注意, notes for use).
• 〜にあたって／〜にあたり (ni atatte / ni atari) - “on the occasion of, as we face”. Slightly forward-looking: it introduces what you do in preparation for or in greeting of the event: 留学するにあたって、必要な書類を集めました。
• 〜に先立って／〜に先立ち (ni sakidatte / ni sakidachi, adnominal に先立つ) - prior to, strictly before: 開会に先立ち、説明会を行います。

Step 2 - Extent and span: 〜にわたって and friends. 〜にわたって／〜にわたり (ni watatte / ni watari) says a thing stretches across a period, an area or a number of items. It needs a measurable span in front: 三年, 全国, 十回. The adnominal 〜にわたる is even more common in headlines: 三年にわたる調査 (sannen ni wataru chōsa, a three-year survey).

Two neighbours: 〜からなる (kara naru, “consists of”) - 十人からなるチーム (jūnin kara naru chīmu, a team made up of ten people); and 〜に及ぶ (ni oyobu, “reaching as far as”, usually of a surprising quantity) - 五時間に及ぶ会議 (gojikan ni oyobu kaigi, a meeting running to five hours).

Step 3 - 〜を通じて vs 〜を通して. Both take を, and both mean either “throughout” (a span) or “via” (a medium). The difference is one of feel, and it is small:

• 〜を通じて (o tsūjite) is the more written, more impersonal one, and is the usual choice for throughout a whole period or area: 一年を通じて (ichinen o tsūjite, all year round).
• 〜を通して (o tōshite) foregrounds actively using something as a route, so it wins with a person or a concrete channel: 友人を通して連絡しました。

For a span, both are heard; for “through the good offices of someone”, prefer を通して. Note the different reading of the same kanji 通 - つう in を通じて, とお in を通して.

Step 4 - 次第 is three separate patterns. Learners conflate them constantly. The cure is to look at what stands in front of 次第:

1. V-ます-stem + 次第 = as soon as. 書類が届き次第、手続きを始めます。 Two hard restrictions: the stem is never a past form (×届きました次第), and the following clause cannot be past - this pattern only announces something still to come, so it ends in 〜ます, 〜てください, 〜つもりです. For a past sequence use 〜たらすぐに (lesson 24).
2. Noun + 次第だ／次第で(は) = it depends on. No particle before it: 明日の予定は天気次第です。 With で it becomes adverbial: 相手次第で結果が変わります (Aite shidai de kekka ga kawarimasu, the outcome changes depending on the other party).
3. Plain clause + 次第です = the formal “that is how the situation stands”, a humble way of explaining a background in business speech: こうしてご連絡した次第です。 This one is a noun predicate about a reason, not about a dependency.

Step 5 - Irrespectiveness: it does not matter which. These say the outcome is the same across every value of something:

• Noun + を問わず (o towazu, literally “without asking”) - the job-ad favourite: 経験を問わず, 年齢・性別を問わず, 昼夜を問わず.
• Noun + にかかわらず／にかかわりなく (ni kakawarazu / ni kakawari naku) - same job, and it also accepts a pair of opposites or an embedded question: 行く行かないにかかわらず, 参加するかどうかにかかわらず.
• Noun + の + いかんによらず／いかんにかかわらず (no ikan ni yorazu / no ikan ni kakawarazu) - the stiffest, contract-only version: 理由のいかんによらず返金できません。

Step 6 - にかかわらず is NOT にもかかわらず. This is the single most common error in the whole lesson. 〜にもかかわらず (ni mo kakawarazu) is a concession: one actual fact happened, and the result went against it - despite. It belongs to lesson 59, not here.

天候にかかわらず試合をします = we play in any weather. 雨だったにもかかわらず試合をしました = it rained, and we played anyway.

Step 7 - Adaptation and basis: things that DO vary. The mirror image of Step 5. All take に except をもとに:

• 〜に応じて (ni ōjite, adnominal に応じた) - varying in accordance with: 収入に応じて税金が決まります。
• 〜に沿って (ni sotte, adnominal に沿った) - in line with a plan, policy or wish: 方針に沿って進めます。
• 〜に基づいて (ni motozuite, adnominal に基づく) - on the basis of data, facts, law: 事実に基づく報道。
• 〜をもとに(して) (o moto ni shite, adnominal をもとにした) - using something as raw material: 実話をもとにした映画。

に応じて and に基づいて are close: に応じて implies the result changes case by case; に基づいて implies one fixed source everything is derived from.

Step 8 - Written variants you only need to read. 〜における／〜において (ni okeru / ni oite) is a formal で or に (日本における教育); 〜にて (nite) is a formal で of place or means (会議室にて、メールにて); 〜をめぐって (o megutte) is “over, surrounding” a dispute (see lesson 55). Never say these to a friend - they read as a form being recited aloud.

Forms & patterns

Occasion and juncture - all take a bare noun or a dictionary form:

Extent and span:

The three 次第 patterns - identify by what stands in front:

Regardless vs depending on - the two opposite families:

Basis and written variants:

Examples

Common mistakes

• 経験にもかかわらず応募できます。 (Keiken ni mo kakawarazu ōbo dekimasu.) -> 経験を問わず応募できます。 (Keiken o towazu ōbo dekimasu.) - にもかかわらず means “despite one known fact”; for “any value is fine” use を問わず／にかかわらず. The も is what flips the meaning.
• 到着しました次第、ご連絡します。 (Tōchaku shimashita shidai, go-renraku shimasu.) -> 到着次第、ご連絡します。 (Tōchaku shidai, go-renraku shimasu.) - “as soon as” 次第 attaches to a ます-stem or a する-noun, never to a past form.
• 駅に着き次第、電話しました。 (Eki ni tsuki shidai, denwa shimashita.) -> 駅に着いたらすぐに電話しました。 (Eki ni tsuitara sugu ni denwa shimashita.) - the clause after ます-stem + 次第 must be future; a past sequence needs 〜たらすぐに.
• 三年をわたる調査 (sannen o wataru chōsa) -> 三年にわたる調査 (sannen ni wataru chōsa) - にわたる takes に. を belongs to を通じて, を問わず and をもとに; mixing the particles is the fastest way to be misread.
• 収入にかかわらず税金が変わります。 (Shūnyū ni kakawarazu zeikin ga kawarimasu.) -> 収入に応じて税金が変わります。 (Shūnyū ni ōjite zeikin ga kawarimasu.) - にかかわらず says the outcome does not vary, so it contradicts an affirmative 変わります; when the result really does track the noun, use に応じて.

Tips

• Sort the whole lesson by particle. に-items are junctures and adaptation (に際して, にあたって, に先立って, にわたって, に応じて, に沿って, に基づいて); を-items are “through” and “regardless” (を通じて, を通して, を問わず, をもとに). Getting the particle right is 80% of the marks.
• One kana, opposite meanings: にかかわらず = regardless, にもかかわらず = despite. Mnemonic: the も is the “even though” - it adds the fact you are conceding.
• For 次第, look left, not right. ます-stem -> “as soon as”. Bare noun -> “depends on”. Full clause -> “such is the situation”. The three never overlap, because nothing else can occupy that slot.
• These live in print, not in speech. In conversation they thin out to A2 grammar: に際して -> とき, にわたって -> 〜の間, にかかわらず -> 〜ても, 次第 -> 〜たらすぐに. Recognise them in a job posting; produce them in formal email and writing.