유기금속촉매를 이용한 유기반응 개발: Part I. 촉매적 알코올 활성화 전략을 이용한 아마이드 합성 Part II. 가시광선 광촉매를 이용한 C(sp3)-H 결합 활성화

학위논문 (박사)-- 서울대학교 대학원 : 자연과학대학 화학부, 2018. 8. Soon Hyeok Hong.The research described in this thesis covers development of new organic reactions catalyzed by organometallic complexes. The thesis is divided into two parts according to the catalytic strategy used. Part I introduces a new catalytic amide synthetic method utilizing dehydrogenative alcohol activation strategy. It is atom-economical and environmentally benign alternative of classical amide synthetic strategies. The basic concept of the strategy and state-of-the-art examples are discussed in Chapter 1. 100% atom economical amide synthesis using alcohols and nitriles as reactant is achieved with N-heterocyclic carbene (NHC) coordinated ruthenium catalyst (Chapter 2). NHC-dihydridoruthenium complex is proposed as the active catalytic species, and the involvement of unusual imine intermediate is suggested based on the mechanistic studies. Methanol is a promising C1 building block due to its low toxicity, low cost, and worldwide stabilized production. With well-defined NHC-dihydridoruthenium catalyst, N-formamide is synthesized from either nitrile or amine utilizing methanol as a formylating source (Chapter 3). No extra base or hydrogen acceptor is required. Part II describes C(sp3)−H activation reactions mediated by visible light photoredox catalysis. C(sp3)−H functionalization is an ideal process in organic chemistry. Recent advance in visible light photoredox catalysis enables selective and efficient C(sp3)−H activation reactions. The concept of the strategy and representative examples are summarized in Chapter 4. Thioesters are versatile synthetic building blocks of complex molecule synthesis and peptide synthesis. The photoredox mediated nickel catalyzed ethereal C(sp3)−H thiocarbonylation reaction is reported (Chapter 5). It is not only the first C(sp3)–H thiocarbonylation reaction, but also the first example of utilizing simple aryl thioester as a thiocarbonylation source instead of CO gas and thiol. Photocatalytic single electron reduction and fragmentation of the thioester is proposed as the key mechanism of the reaction.Abstract 1 Table of Contents 4 List of Tables 8 List of Schemes 9 List of Figures 12 Appendix 186 Abstract in Koreans 277 Part I. Amide Synthesis Using Catalytic Alcohol Activation Strategy 13 Chapter 1. Amide Synthesis from Alcohol and Amine Using Dehydrogenative Alcohol Activation Strategy 13 1.1 Introduction 13 1.2 Conventional amide bond synthesis 13 1.3 Amide synthesis with catalytic dehydrogenative alcohol activation 16 1.3.1 Dehydrogenative alcohol activation 16 1.3.2 Amide synthesis with catalytic dehydrogenative alcohol activation: Ru and Rh based catalysts 20 1.3.3 Amide synthesis with catalytic dehydrogenative alcohol activation: Fe and Mn based catalysts 31 1.4 Conclusion 34 1.5 References 35 Chapter 2. Ruthenium-Catalyzed Redox-Neutral and Single-Step Amide Synthesis from Alcohol and Nitrile with Complete Atom Economy 39 2.1 Introduction 39 2.2 Results and discussion 41 2.2.1 Optimization for amide synthesis from alcohol and nitrile 41 2.2.2 Substrate scope 43 2.2.3 Mechanistic studies 49 2.3 Conclusion 54 2.4 Experimental section 54 2.4.1 General information 54 2.4.2 General procedure for amide synthesis from nitrile and alcohol 55 2.4.3 Procedure for deuterium labeling study 56 2.4.4 GC analysis for reaction intermediate detection 56 2.4.5 1H NMR experiment for benzaldimine intermediate observation 58 2.4.6 Characterization of newly reported compounds 62 2.5 References 69 Chapter 3. Hydrogen Acceptor- and Base-Free N-Formylation of Nitriles and Amines Using Methanol as C1 Source 72 3.1 Introduction 72 3.2 Results and discussion 75 3.2.1 Reaction condition optimization 75 3.2.2 Substrate scope of nitrile 78 3.2.3 Mechanistic studies 81 3.2.4 Substrate scope of amine 83 3.3 Conclusion 86 3.4 Experimental section 87 3.4.1 General information 87 3.4.2 General procedure for N-formamide synthesis from nitrile and methanol 87 3.4.3 General procedure for N-formamide synthesis from amine and methanol 88 3.4.4 Investigation of reaction intermediates 88 3.4.5 Characterization of newly reported compounds 89 3.5 References 97 Part II. Visible Light Photoredox Catalyst Mediated C(sp3) H Functionalization 100 Chapter 4. Visible Light Photoredox Catalysis for C(sp3)H Functionalization 100 4.1 Introduction 100 4.2 Concept and general mechanism of visible light photoredox catalysis 101 4.3 Visible light photoredox α-amino C(sp3)H functionalization 105 4.4 Visible light photoredox C(sp3)H functionalization with hydrogen atom transfer (HAT) catalysis 114 4.5 Visible light photoredox C(sp3)H functionalization with transition metal catalysis 118 4.6 Visible light photoredox/transition metal/HAT triple catalysis 124 4.7 Conclusion 126 4.8 References 127 Chapter 5. Photoredox Mediated Nickel Catalyzed C(sp3)H Thiocarbonylation of Ethers 132 5.1 Introduction 132 5.2 Results and discussion 134 5.2.1 Optimization for α-oxy thiocarbonylation reaction 134 5.2.2 Substrate scope of thioesters 136 5.2.3 Substrate scope of ethers 138 5.2.4 Mechanistic studies 139 5.3 Conclusion 147 5.4 Experimental section 148 5.4.1 General information 149 5.4.2 General procedure for reactant thioester synthesis 150 5.4.3 General procedure for C(sp3)H thiocarbonylation reactions 150 5.4.4 Procedure for 13CO incorporation experiment 151 5.4.5 Deuterium incorporation experiment 154 5.4.6 Synthesis and characterization of nickel complexes 155 5.4.7 Cyclic voltammetry (CV) studies 157 5.4.8 Characterization of newly reported compounds 161 5.5 References 182 Docto

셀룰라 네트워크 사이드링크 채널에서의 지능적 자원 관리 기법 연구

학위논문(박사)--서울대학교 대학원 :공과대학 전기·정보공학부,2020. 2. 박세웅.셀룰러 네트워크에서 사이드링크 통신이란 기기 간 직접 통신을 뜻한다. 이 사이드링크 통신의 장점으로는 주파수 효율 증대와 낮은 end-to-end 지연시간, 그리고 네트워크 커버리지 밖에서도 동작 가능하다는 점이 있으며 대표적인 기술로는 기기 간 통신인 D2D 통신과 차량 간 통신인 V2V가 있다. 하지만 사용 가능한 자원이 한정적이고 경우에 따라서는 기기가 기지국의 도움 없이 스스로 자원 선택을 해야 하기 때문에 한정된 자원 및 정보를 바탕으로 효율적인 자원 관리가 필요하고 이에 따른 자원 할당 기법을 제안한다. 첫째, 기지국의 트래픽이 과도하게 발생했을 경우 면허대역과 비면허대역 D2D 통신을 활용해 트래픽 오프로딩을 하는 상황을 다룬다. 이때 비면허대역 D2D 통신의 경우 와이파이 기기들과 공존하면서 서비스 품질을 보장해야 하는데, 이를 위한 밴드 스위칭 기법을 제안하고 이에 따른 시스템 캐패시티 증대를 Markov process 분석을 이용해 수학적으로 분석한다. 또한 시뮬레이션을 통해 분석값의 정확성과 기존 기법 대비 성능 향상을 검증한다. 두 번째로, 각 기기들이 모빌리티를 갖는 차량 간 통신 환경에서 각 차량들이 이웃들에게 주기적으로 상태 보고 메시지를 브로드캐스트하는 상황을 다룬다. 이때 차량들이 과도하게 밀집한다면 차량 간 통신에서 가장 중요한 reliability가 현저히 저하되는 현상을 관찰하였고, 이에 따라 센싱 정보 기반 메시지 간격 조절 및 전송 파워 조절 기법인 C-V2X 기반 ATOMIC을 제안한다. 간단한 분석과 트레이스 기반 시뮬레이션을 통해 도심 환경과 고속도로 환경 모두에서 표준 기법에 비해 상당한 성능 향상을 보이는 것을 확인한다. 세 번째 주제는 주기적인 메시지뿐 아니라 멀티 홉으로 전달되는 비주기적 사고 정보를 담은 메시지까지 혼재한 상황을 다룬다. 이렇게 복잡하고 다이나믹한 환경에서는 채널에 대한 불확실성이 높아지기 때문에 기존의 최적화 문제를 적용하는 데 어려움이 있다. 이에 따라 기계 학습을 활용한 분산적인 자원 할당 기법을 제안한다. 각 차량들은 DQN을 활용해 관찰 정보를 토대로 미래의 리워드를 최대화하는 자원, 전송 파워, 그리고 어떤 메시지를 릴레이 할지를 결정한다. 적절한 리워드 설계를 통해 기존 기법 대비 CAM의 PRR과 DENM의 확산을 크게 개선하는 것을 보여준다.Sidelink communications in cellular network are a communication that is directly done between users. It provides increased spectral efficiency, shortens end-to-end transmission latency, and enables out-of-network coverage operation. There are two representative sidelink communications which are device-to-device (D2D) communications and vehicle-to-vehicle (V2V) communications. Firstly, we propose a traffic steering scheme that jointly exploits three types of transmission links: cellular links, D2D links on licensed bands, and D2D links on unlicensed bands. We first present an analytical framework and model the proposed traffic steering scheme by using Markov analysis. We verify the analytical framework and confirm that the proposed scheme that uses the licensed and unlicensed bands outperforms the conventional scheme that uses the licensed bands only through simulation. Secondly, we propose ATOMIC, an Adaptive Transmission pOwer and Message Interval Control scheme for C-V2X Mode 4, in which each vehicle utilizes real-time channel sensing and neighbor information to reduce channel contention for improved reliability and latency. Through analysis and extensive simulations, we show that ATOMIC outperforms the standard Mode 4 in both urban and highway scenarios especially in highly dense environments. Lastly, we investigate a spectrum sharing problem in vehicular networks based on multi-agent reinforcement learning where periodic and non-periodic messages share the same resource pools. Fast channel variations in high mobility vehicular environments preclude the possibility of collecting accurate instantaneous channel state information at the base station for centralized resource management. As a solution, we formulate the resource sharing as a multi-agent reinforcement learning problem, which is then solved by using a fingerprint-based deep Q-network method. Each vehicle collectively interacts with the communication environment, receives distinctive observations and rewards, and learns to improve spectrum, power allocation, and a choice of messages to relay through updating Q-networks that utilizes the gained experiences. We demonstrate that the multiple vehicles successfully learn with a proper reward design and training mechanism to cooperate in a distributed way to simultaneously improve the PRR of CAM and the dissemination ratio of DENM.1 INTRODUCTION 1 1.1 Sidelink Communication 2 1.1.1 D2D Communication 2 1.1.2 V2X Communication 2 1.2 Contributions and Outline 2 2 D2D Communications Underlaying Cellular Networks on Licensed and Unlicensed Bands with QoS Constraints 4 2.1 Introduction 4 2.2 Related Work 7 2.3 System Model 9 2.3.1 Network Model 9 2.3.2 Traffic and Service Model 11 2.3.3 Channel Model and QoS Requirements 11 2.4 Traffic Steering Scheme 13 2.4.1 Mode Selection 13 2.4.2 Band Selection 13 2.4.3 Channel Selection 14 2.4.4 Admission Control 14 2.4.5 Traffic Re-steering onto Licensed Bands 16 2.5 Stochastic Analysis 16 2.5.1 Licensed Band Operations 17 2.5.2 Unlicensed Band Operations 21 2.5.3 Re-steered Sessions 28 2.5.4 WLAN Performance Degradation 30 2.6 Performance Evaluation 32 2.7 Summary 39 3 ATOMIC: An Adaptive Transmission Power and Message Interval Control Scheme for Cellular V2X Mode 4 40 3.1 Introduction 40 3.2 Related Work 43 3.3 Background 45 3.3.1 C-V2X Mode 4 45 3.3.2 Safety Requirements 47 3.4 Problem and Motivation 48 3.5 Proposed Design 50 3.5.1 Message Interval Control Algorithm 51 3.5.2 Power Adaptation Algorithm 54 3.5.3 ATOMIC 58 3.6 Evaluation 59 3.6.1 Simulation setup and performance metrics 59 3.6.2 Average PRR 60 3.6.3 Tail UD 63 3.6.4 CAM range 64 3.7 Summary 65 4 Joint Transmission of Periodic and Non-Periodic Messages in C-V2X Using Multi-Agent Deep Reinforcement Learning 66 4.1 Introduction 66 4.2 Background 69 4.2.1 Cellular V2X 69 4.2.2 Safety Message 70 4.3 Problem Statement and Motivation 71 4.3.1 System model 71 4.3.2 Motivation 73 4.4 Multi-Agent RL Based Resource Allocation 74 4.4.1 State and Observation Space 74 4.4.2 Action Space 76 4.4.3 Reward Design 76 4.4.4 Learning Algorithm 78 4.5 Evaluation 80 4.6 Summary 86 5 Conclusion 87 Abstract (In Korean) 98 Acknowlegement 100Docto